diff --git a/embassy-executor/build.rs b/embassy-executor/build.rs
index 8af8ccaf3..8a41d7503 100644
--- a/embassy-executor/build.rs
+++ b/embassy-executor/build.rs
@@ -3,7 +3,7 @@ use std::fmt::Write;
 use std::path::PathBuf;
 use std::{env, fs};
 
-#[path = "../build_common.rs"]
+#[path = "./build_common.rs"]
 mod common;
 
 static CONFIGS: &[(&str, usize)] = &[
diff --git a/build_common.rs b/embassy-executor/build_common.rs
similarity index 86%
rename from build_common.rs
rename to embassy-executor/build_common.rs
index eda83f25d..2c65f8529 100644
--- a/build_common.rs
+++ b/embassy-executor/build_common.rs
@@ -1,3 +1,11 @@
+// NOTE: this file is copy-pasted between several Embassy crates, because there is no
+// straightforward way to share this code:
+// - it cannot be placed into the root of the repo and linked from each build.rs using `#[path =
+// "../build_common.rs"]`, because `cargo publish` requires that all files published with a crate
+// reside in the crate's directory,
+// - it cannot be symlinked from `embassy-xxx/build_common.rs` to `../build_common.rs`, because
+// symlinks don't work on Windows.
+
 use std::collections::HashSet;
 use std::env;
 use std::ffi::OsString;
diff --git a/embassy-hal-internal/build.rs b/embassy-hal-internal/build.rs
index 2649f5d37..ecd2c0c9f 100644
--- a/embassy-hal-internal/build.rs
+++ b/embassy-hal-internal/build.rs
@@ -1,4 +1,4 @@
-#[path = "../build_common.rs"]
+#[path = "./build_common.rs"]
 mod common;
 
 fn main() {
diff --git a/embassy-hal-internal/build_common.rs b/embassy-hal-internal/build_common.rs
new file mode 100644
index 000000000..2c65f8529
--- /dev/null
+++ b/embassy-hal-internal/build_common.rs
@@ -0,0 +1,109 @@
+// NOTE: this file is copy-pasted between several Embassy crates, because there is no
+// straightforward way to share this code:
+// - it cannot be placed into the root of the repo and linked from each build.rs using `#[path =
+// "../build_common.rs"]`, because `cargo publish` requires that all files published with a crate
+// reside in the crate's directory,
+// - it cannot be symlinked from `embassy-xxx/build_common.rs` to `../build_common.rs`, because
+// symlinks don't work on Windows.
+
+use std::collections::HashSet;
+use std::env;
+use std::ffi::OsString;
+use std::process::Command;
+
+/// Helper for emitting cargo instruction for enabling configs (`cargo:rustc-cfg=X`) and declaring
+/// them (`cargo:rust-check-cfg=cfg(X)`).
+#[derive(Debug)]
+pub struct CfgSet {
+    enabled: HashSet<String>,
+    declared: HashSet<String>,
+    emit_declared: bool,
+}
+
+impl CfgSet {
+    pub fn new() -> Self {
+        Self {
+            enabled: HashSet::new(),
+            declared: HashSet::new(),
+            emit_declared: is_rustc_nightly(),
+        }
+    }
+
+    /// Enable a config, which can then be used in `#[cfg(...)]` for conditional compilation.
+    ///
+    /// All configs that can potentially be enabled should be unconditionally declared using
+    /// [`Self::declare()`].
+    pub fn enable(&mut self, cfg: impl AsRef<str>) {
+        if self.enabled.insert(cfg.as_ref().to_owned()) {
+            println!("cargo:rustc-cfg={}", cfg.as_ref());
+        }
+    }
+
+    pub fn enable_all(&mut self, cfgs: &[impl AsRef<str>]) {
+        for cfg in cfgs.iter() {
+            self.enable(cfg.as_ref());
+        }
+    }
+
+    /// Declare a valid config for conditional compilation, without enabling it.
+    ///
+    /// This enables rustc to check that the configs in `#[cfg(...)]` attributes are valid.
+    pub fn declare(&mut self, cfg: impl AsRef<str>) {
+        if self.declared.insert(cfg.as_ref().to_owned()) && self.emit_declared {
+            println!("cargo:rustc-check-cfg=cfg({})", cfg.as_ref());
+        }
+    }
+
+    pub fn declare_all(&mut self, cfgs: &[impl AsRef<str>]) {
+        for cfg in cfgs.iter() {
+            self.declare(cfg.as_ref());
+        }
+    }
+
+    pub fn set(&mut self, cfg: impl Into<String>, enable: bool) {
+        let cfg = cfg.into();
+        if enable {
+            self.enable(cfg.clone());
+        }
+        self.declare(cfg);
+    }
+}
+
+fn is_rustc_nightly() -> bool {
+    let rustc = env::var_os("RUSTC").unwrap_or_else(|| OsString::from("rustc"));
+
+    let output = Command::new(rustc)
+        .arg("--version")
+        .output()
+        .expect("failed to run `rustc --version`");
+
+    String::from_utf8_lossy(&output.stdout).contains("nightly")
+}
+
+/// Sets configs that describe the target platform.
+pub fn set_target_cfgs(cfgs: &mut CfgSet) {
+    let target = env::var("TARGET").unwrap();
+
+    if target.starts_with("thumbv6m-") {
+        cfgs.enable_all(&["cortex_m", "armv6m"]);
+    } else if target.starts_with("thumbv7m-") {
+        cfgs.enable_all(&["cortex_m", "armv7m"]);
+    } else if target.starts_with("thumbv7em-") {
+        cfgs.enable_all(&["cortex_m", "armv7m", "armv7em"]);
+    } else if target.starts_with("thumbv8m.base") {
+        cfgs.enable_all(&["cortex_m", "armv8m", "armv8m_base"]);
+    } else if target.starts_with("thumbv8m.main") {
+        cfgs.enable_all(&["cortex_m", "armv8m", "armv8m_main"]);
+    }
+    cfgs.declare_all(&[
+        "cortex_m",
+        "armv6m",
+        "armv7m",
+        "armv7em",
+        "armv8m",
+        "armv8m_base",
+        "armv8m_main",
+    ]);
+
+    cfgs.set("has_fpu", target.ends_with("-eabihf"));
+}
diff --git a/embassy-stm32/build.rs b/embassy-stm32/build.rs
index c7b2ea63a..6aedcc228 100644
--- a/embassy-stm32/build.rs
+++ b/embassy-stm32/build.rs
@@ -13,7 +13,7 @@ use stm32_metapac::metadata::{
     ALL_PERIPHERAL_VERSIONS, METADATA,
 };
 
-#[path = "../build_common.rs"]
+#[path = "./build_common.rs"]
 mod common;
 
 fn main() {
diff --git a/embassy-stm32/build_common.rs b/embassy-stm32/build_common.rs
new file mode 100644
index 000000000..2c65f8529
--- /dev/null
+++ b/embassy-stm32/build_common.rs
@@ -0,0 +1,109 @@
+// NOTE: this file is copy-pasted between several Embassy crates, because there is no
+// straightforward way to share this code:
+// - it cannot be placed into the root of the repo and linked from each build.rs using `#[path =
+// "../build_common.rs"]`, because `cargo publish` requires that all files published with a crate
+// reside in the crate's directory,
+// - it cannot be symlinked from `embassy-xxx/build_common.rs` to `../build_common.rs`, because
+// symlinks don't work on Windows.
+
+use std::collections::HashSet;
+use std::env;
+use std::ffi::OsString;
+use std::process::Command;
+
+/// Helper for emitting cargo instruction for enabling configs (`cargo:rustc-cfg=X`) and declaring
+/// them (`cargo:rust-check-cfg=cfg(X)`).
+#[derive(Debug)]
+pub struct CfgSet {
+    enabled: HashSet<String>,
+    declared: HashSet<String>,
+    emit_declared: bool,
+}
+
+impl CfgSet {
+    pub fn new() -> Self {
+        Self {
+            enabled: HashSet::new(),
+            declared: HashSet::new(),
+            emit_declared: is_rustc_nightly(),
+        }
+    }
+
+    /// Enable a config, which can then be used in `#[cfg(...)]` for conditional compilation.
+    ///
+    /// All configs that can potentially be enabled should be unconditionally declared using
+    /// [`Self::declare()`].
+    pub fn enable(&mut self, cfg: impl AsRef<str>) {
+        if self.enabled.insert(cfg.as_ref().to_owned()) {
+            println!("cargo:rustc-cfg={}", cfg.as_ref());
+        }
+    }
+
+    pub fn enable_all(&mut self, cfgs: &[impl AsRef<str>]) {
+        for cfg in cfgs.iter() {
+            self.enable(cfg.as_ref());
+        }
+    }
+
+    /// Declare a valid config for conditional compilation, without enabling it.
+    ///
+    /// This enables rustc to check that the configs in `#[cfg(...)]` attributes are valid.
+    pub fn declare(&mut self, cfg: impl AsRef<str>) {
+        if self.declared.insert(cfg.as_ref().to_owned()) && self.emit_declared {
+            println!("cargo:rustc-check-cfg=cfg({})", cfg.as_ref());
+        }
+    }
+
+    pub fn declare_all(&mut self, cfgs: &[impl AsRef<str>]) {
+        for cfg in cfgs.iter() {
+            self.declare(cfg.as_ref());
+        }
+    }
+
+    pub fn set(&mut self, cfg: impl Into<String>, enable: bool) {
+        let cfg = cfg.into();
+        if enable {
+            self.enable(cfg.clone());
+        }
+        self.declare(cfg);
+    }
+}
+
+fn is_rustc_nightly() -> bool {
+    let rustc = env::var_os("RUSTC").unwrap_or_else(|| OsString::from("rustc"));
+
+    let output = Command::new(rustc)
+        .arg("--version")
+        .output()
+        .expect("failed to run `rustc --version`");
+
+    String::from_utf8_lossy(&output.stdout).contains("nightly")
+}
+
+/// Sets configs that describe the target platform.
+pub fn set_target_cfgs(cfgs: &mut CfgSet) {
+    let target = env::var("TARGET").unwrap();
+
+    if target.starts_with("thumbv6m-") {
+        cfgs.enable_all(&["cortex_m", "armv6m"]);
+    } else if target.starts_with("thumbv7m-") {
+        cfgs.enable_all(&["cortex_m", "armv7m"]);
+    } else if target.starts_with("thumbv7em-") {
+        cfgs.enable_all(&["cortex_m", "armv7m", "armv7em"]);
+    } else if target.starts_with("thumbv8m.base") {
+        cfgs.enable_all(&["cortex_m", "armv8m", "armv8m_base"]);
+    } else if target.starts_with("thumbv8m.main") {
+        cfgs.enable_all(&["cortex_m", "armv8m", "armv8m_main"]);
+    }
+    cfgs.declare_all(&[
+        "cortex_m",
+        "armv6m",
+        "armv7m",
+        "armv7em",
+        "armv8m",
+        "armv8m_base",
+        "armv8m_main",
+    ]);
+
+    cfgs.set("has_fpu", target.ends_with("-eabihf"));
+}
diff --git a/embassy-sync/build.rs b/embassy-sync/build.rs
index 2649f5d37..ecd2c0c9f 100644
--- a/embassy-sync/build.rs
+++ b/embassy-sync/build.rs
@@ -1,4 +1,4 @@
-#[path = "../build_common.rs"]
+#[path = "./build_common.rs"]
 mod common;
 
 fn main() {
diff --git a/embassy-sync/build_common.rs b/embassy-sync/build_common.rs
new file mode 100644
index 000000000..2c65f8529
--- /dev/null
+++ b/embassy-sync/build_common.rs
@@ -0,0 +1,109 @@
+// NOTE: this file is copy-pasted between several Embassy crates, because there is no
+// straightforward way to share this code:
+// - it cannot be placed into the root of the repo and linked from each build.rs using `#[path =
+// "../build_common.rs"]`, because `cargo publish` requires that all files published with a crate
+// reside in the crate's directory,
+// - it cannot be symlinked from `embassy-xxx/build_common.rs` to `../build_common.rs`, because
+// symlinks don't work on Windows.
+
+use std::collections::HashSet;
+use std::env;
+use std::ffi::OsString;
+use std::process::Command;
+
+/// Helper for emitting cargo instruction for enabling configs (`cargo:rustc-cfg=X`) and declaring
+/// them (`cargo:rust-check-cfg=cfg(X)`).
+#[derive(Debug)]
+pub struct CfgSet {
+    enabled: HashSet<String>,
+    declared: HashSet<String>,
+    emit_declared: bool,
+}
+
+impl CfgSet {
+    pub fn new() -> Self {
+        Self {
+            enabled: HashSet::new(),
+            declared: HashSet::new(),
+            emit_declared: is_rustc_nightly(),
+        }
+    }
+
+    /// Enable a config, which can then be used in `#[cfg(...)]` for conditional compilation.
+    ///
+    /// All configs that can potentially be enabled should be unconditionally declared using
+    /// [`Self::declare()`].
+    pub fn enable(&mut self, cfg: impl AsRef<str>) {
+        if self.enabled.insert(cfg.as_ref().to_owned()) {
+            println!("cargo:rustc-cfg={}", cfg.as_ref());
+        }
+    }
+
+    pub fn enable_all(&mut self, cfgs: &[impl AsRef<str>]) {
+        for cfg in cfgs.iter() {
+            self.enable(cfg.as_ref());
+        }
+    }
+
+    /// Declare a valid config for conditional compilation, without enabling it.
+    ///
+    /// This enables rustc to check that the configs in `#[cfg(...)]` attributes are valid.
+    pub fn declare(&mut self, cfg: impl AsRef<str>) {
+        if self.declared.insert(cfg.as_ref().to_owned()) && self.emit_declared {
+            println!("cargo:rustc-check-cfg=cfg({})", cfg.as_ref());
+        }
+    }
+
+    pub fn declare_all(&mut self, cfgs: &[impl AsRef<str>]) {
+        for cfg in cfgs.iter() {
+            self.declare(cfg.as_ref());
+        }
+    }
+
+    pub fn set(&mut self, cfg: impl Into<String>, enable: bool) {
+        let cfg = cfg.into();
+        if enable {
+            self.enable(cfg.clone());
+        }
+        self.declare(cfg);
+    }
+}
+
+fn is_rustc_nightly() -> bool {
+    let rustc = env::var_os("RUSTC").unwrap_or_else(|| OsString::from("rustc"));
+
+    let output = Command::new(rustc)
+        .arg("--version")
+        .output()
+        .expect("failed to run `rustc --version`");
+
+    String::from_utf8_lossy(&output.stdout).contains("nightly")
+}
+
+/// Sets configs that describe the target platform.
+pub fn set_target_cfgs(cfgs: &mut CfgSet) {
+    let target = env::var("TARGET").unwrap();
+
+    if target.starts_with("thumbv6m-") {
+        cfgs.enable_all(&["cortex_m", "armv6m"]);
+    } else if target.starts_with("thumbv7m-") {
+        cfgs.enable_all(&["cortex_m", "armv7m"]);
+    } else if target.starts_with("thumbv7em-") {
+        cfgs.enable_all(&["cortex_m", "armv7m", "armv7em"]);
+    } else if target.starts_with("thumbv8m.base") {
+        cfgs.enable_all(&["cortex_m", "armv8m", "armv8m_base"]);
+    } else if target.starts_with("thumbv8m.main") {
+        cfgs.enable_all(&["cortex_m", "armv8m", "armv8m_main"]);
+    }
+    cfgs.declare_all(&[
+        "cortex_m",
+        "armv6m",
+        "armv7m",
+        "armv7em",
+        "armv8m",
+        "armv8m_base",
+        "armv8m_main",
+    ]);
+
+    cfgs.set("has_fpu", target.ends_with("-eabihf"));
+}