diff --git a/src/bootstrap/CHANGELOG.md b/src/bootstrap/CHANGELOG.md
index 4105fa5ec96..4381e51ca22 100644
--- a/src/bootstrap/CHANGELOG.md
+++ b/src/bootstrap/CHANGELOG.md
@@ -46,6 +46,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Add `--keep-stage-std`, which behaves like `keep-stage` but allows the stage
   0 compiler artifacts (i.e., stage1/bin/rustc) to be rebuilt if changed
   [#77120](https://github.com/rust-lang/rust/pull/77120).
+- File locking is now used to avoid collisions between multiple running instances of `x.py` (e.g. when using `rust-analyzer` and `x.py` at the same time). Note that Solaris and possibly other non Unix and non Windows systems don't support it [#108607](https://github.com/rust-lang/rust/pull/108607). This might possibly lead to build data corruption.
 
 
 ## [Version 1] - 2020-09-11
diff --git a/src/bootstrap/Cargo.toml b/src/bootstrap/Cargo.toml
index 663987f113c..afe3fc1741b 100644
--- a/src/bootstrap/Cargo.toml
+++ b/src/bootstrap/Cargo.toml
@@ -32,7 +32,6 @@ test = false
 [dependencies]
 build_helper = { path = "../tools/build_helper" }
 cmake = "0.1.38"
-fd-lock = "3.0.8"
 filetime = "0.2"
 getopts = "0.2.19"
 cc = "1.0.69"
@@ -56,6 +55,10 @@ walkdir = "2"
 # Dependencies needed by the build-metrics feature
 sysinfo = { version = "0.26.0", optional = true }
 
+# Solaris doesn't support flock() and thus fd-lock is not option now
+[target.'cfg(not(target_os = "solaris"))'.dependencies]
+fd-lock = "3.0.8"
+
 [target.'cfg(windows)'.dependencies.winapi]
 version = "0.3"
 features = [
diff --git a/src/bootstrap/bin/main.rs b/src/bootstrap/bin/main.rs
index 3856bb64fb3..018f862fae3 100644
--- a/src/bootstrap/bin/main.rs
+++ b/src/bootstrap/bin/main.rs
@@ -7,15 +7,18 @@
 
 use std::env;
 
-use bootstrap::{t, Build, Config, Subcommand, VERSION};
+#[cfg(all(any(unix, windows), not(target_os = "solaris")))]
+use bootstrap::t;
+use bootstrap::{Build, Config, Subcommand, VERSION};
 
 fn main() {
     let args = env::args().skip(1).collect::<Vec<_>>();
     let config = Config::parse(&args);
 
-    let mut build_lock;
-    let _build_lock_guard;
-    if cfg!(any(unix, windows)) {
+    #[cfg(all(any(unix, windows), not(target_os = "solaris")))]
+    {
+        let mut build_lock;
+        let _build_lock_guard;
         let path = config.out.join("lock");
         build_lock = fd_lock::RwLock::new(t!(std::fs::File::create(&path)));
         _build_lock_guard = match build_lock.try_write() {
@@ -30,9 +33,9 @@ fn main() {
                 t!(build_lock.write())
             }
         };
-    } else {
-        println!("warning: file locking not supported for target, not locking build directory");
     }
+    #[cfg(any(not(any(unix, windows)), target_os = "solaris"))]
+    println!("warning: file locking not supported for target, not locking build directory");
 
     // check_version warnings are not printed during setup
     let changelog_suggestion =
@@ -125,7 +128,7 @@ fn get_lock_owner(f: &std::path::Path) -> Option<u64> {
     })
 }
 
-#[cfg(not(target_os = "linux"))]
+#[cfg(not(any(target_os = "linux", target_os = "solaris")))]
 fn get_lock_owner(_: &std::path::Path) -> Option<u64> {
     // FIXME: Implement on other OS's
     None