Auto merge of #85531 - luqmana:flip-gc, r=petrochenkov

Swap TargetOptions::linker_is_gnu default from false to true and update targets as appropriate.

#85274 gated the `--gc-sections` flag on targets that specified `linker_is_gnu` to stop us from passing it to incompatible linkers. But that had the unintended effect of the flag no longer being passed on targets for which it is valid and hence caused a regression in binary size. Given that most `ld`-style linkers are GNU compatible, this change flips our default for `linker_is_gnu` from false to true. That also means updating the targets that relied on the previous default:
* Apple
* Illumos
* L4Re (not sure about this one)
* MSVC
* NvtPtx
* Solaris

Fixes #85519

compiler/rustc_target/src/spec/aarch64_unknown_none.rs

@@ -16,7 +16,6 @@ pub fn target() -> Target {
         executables: true,
         relocation_model: RelocModel::Static,
         disable_redzone: true,
-        linker_is_gnu: true,
         max_atomic_width: Some(128),
         panic_strategy: PanicStrategy::Abort,
         unsupported_abis: super::arm_base::unsupported_abis(),

compiler/rustc_target/src/spec/aarch64_unknown_none_softfloat.rs

@@ -16,7 +16,6 @@ pub fn target() -> Target {
         executables: true,
         relocation_model: RelocModel::Static,
         disable_redzone: true,
-        linker_is_gnu: true,
         max_atomic_width: Some(128),
         panic_strategy: PanicStrategy::Abort,
         unsupported_abis: super::arm_base::unsupported_abis(),

compiler/rustc_target/src/spec/apple_base.rs

@@ -22,6 +22,7 @@ pub fn opts(os: &str) -> TargetOptions {
         // macOS has -dead_strip, which doesn't rely on function_sections
         function_sections: false,
         dynamic_linking: true,
+        linker_is_gnu: false,
         executables: true,
         families: vec!["unix".to_string()],
         is_like_osx: true,

compiler/rustc_target/src/spec/avr_gnu_base.rs

@@ -16,7 +16,6 @@ pub fn target(target_cpu: String) -> Target {
 
             linker: Some("avr-gcc".to_owned()),
             executables: true,
-            linker_is_gnu: true,
             eh_frame_header: false,
             pre_link_args: vec![(LinkerFlavor::Gcc, vec![format!("-mmcu={}", target_cpu)])]
                 .into_iter()

compiler/rustc_target/src/spec/dragonfly_base.rs

@@ -6,7 +6,6 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         families: vec!["unix".to_string()],
-        linker_is_gnu: true,
         has_rpath: true,
         position_independent_executables: true,
         relro_level: RelroLevel::Full,

compiler/rustc_target/src/spec/freebsd_base.rs

@@ -6,7 +6,6 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         families: vec!["unix".to_string()],
-        linker_is_gnu: true,
         has_rpath: true,
         position_independent_executables: true,
         eliminate_frame_pointer: false, // FIXME 43575

compiler/rustc_target/src/spec/fuchsia_base.rs

@@ -27,7 +27,6 @@ pub fn opts() -> TargetOptions {
         executables: true,
         families: vec!["unix".to_string()],
         is_like_fuchsia: true,
-        linker_is_gnu: true,
         pre_link_args,
         pre_link_objects: crt_objects::new(&[
             (LinkOutputKind::DynamicNoPicExe, &["Scrt1.o"]),

compiler/rustc_target/src/spec/haiku_base.rs

@@ -7,7 +7,6 @@ pub fn opts() -> TargetOptions {
         executables: true,
         families: vec!["unix".to_string()],
         relro_level: RelroLevel::Full,
-        linker_is_gnu: true,
         ..Default::default()
     }
 }

compiler/rustc_target/src/spec/hermit_base.rs

@@ -13,7 +13,6 @@ pub fn opts() -> TargetOptions {
         linker: Some("rust-lld".to_owned()),
         executables: true,
         has_elf_tls: true,
-        linker_is_gnu: true,
         pre_link_args,
         panic_strategy: PanicStrategy::Abort,
         position_independent_executables: true,

compiler/rustc_target/src/spec/hermit_kernel_base.rs

@@ -14,7 +14,6 @@ pub fn opts() -> TargetOptions {
         linker: Some("rust-lld".to_owned()),
         executables: true,
         has_elf_tls: true,
-        linker_is_gnu: true,
         pre_link_args,
         panic_strategy: PanicStrategy::Abort,
         position_independent_executables: true,

compiler/rustc_target/src/spec/illumos_base.rs

@@ -33,6 +33,7 @@ pub fn opts() -> TargetOptions {
         has_rpath: true,
         families: vec!["unix".to_string()],
         is_like_solaris: true,
+        linker_is_gnu: false,
         limit_rdylib_exports: false, // Linker doesn't support this
         eliminate_frame_pointer: false,
         eh_frame_header: false,

compiler/rustc_target/src/spec/l4re_base.rs

@@ -20,6 +20,7 @@ pub fn opts() -> TargetOptions {
         executables: true,
         panic_strategy: PanicStrategy::Abort,
         linker: Some("ld".to_string()),
+        linker_is_gnu: false,
         families: vec!["unix".to_string()],
         ..Default::default()
     }

compiler/rustc_target/src/spec/linux_base.rs

@@ -6,7 +6,6 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         families: vec!["unix".to_string()],
-        linker_is_gnu: true,
         has_rpath: true,
         position_independent_executables: true,
         relro_level: RelroLevel::Full,

compiler/rustc_target/src/spec/linux_kernel_base.rs

@@ -8,7 +8,6 @@ pub fn opts() -> TargetOptions {
         // don't use probe-stack=inline-asm until rust#83139 and rust#84667 are resolved
         stack_probes: StackProbeType::Call,
         eliminate_frame_pointer: false,
-        linker_is_gnu: true,
         position_independent_executables: true,
         needs_plt: true,
         relro_level: RelroLevel::Full,

compiler/rustc_target/src/spec/mipsel_sony_psp.rs

@@ -21,7 +21,6 @@ pub fn target() -> Target {
             cpu: "mips2".to_string(),
             executables: true,
             linker: Some("rust-lld".to_owned()),
-            linker_is_gnu: true,
             relocation_model: RelocModel::Static,
 
             // PSP FPU only supports single precision floats.

compiler/rustc_target/src/spec/mod.rs

@@ -1086,7 +1086,7 @@ pub struct TargetOptions {
     /// Version of DWARF to use if not using the default.
     /// Useful because some platforms (osx, bsd) only want up to DWARF2.
     pub dwarf_version: Option<u32>,
-    /// Whether the linker support GNU-like arguments such as -O. Defaults to false.
+    /// Whether the linker support GNU-like arguments such as -O. Defaults to true.
     pub linker_is_gnu: bool,
     /// The MinGW toolchain has a known issue that prevents it from correctly
     /// handling COFF object files with more than 2<sup>15</sup> sections. Since each weak
@@ -1307,7 +1307,7 @@ impl Default for TargetOptions {
             is_like_fuchsia: false,
             is_like_wasm: false,
             dwarf_version: None,
-            linker_is_gnu: false,
+            linker_is_gnu: true,
             allows_weak_linkage: true,
             has_rpath: false,
             no_default_libraries: true,

compiler/rustc_target/src/spec/msvc_base.rs

@@ -16,6 +16,7 @@ pub fn opts() -> TargetOptions {
         is_like_windows: true,
         is_like_msvc: true,
         lld_flavor: LldFlavor::Link,
+        linker_is_gnu: false,
         pre_link_args,
         abi_return_struct_as_int: true,
         emit_debug_gdb_scripts: false,

compiler/rustc_target/src/spec/netbsd_base.rs

@@ -6,7 +6,6 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         families: vec!["unix".to_string()],
-        linker_is_gnu: true,
         no_default_libraries: false,
         has_rpath: true,
         position_independent_executables: true,

compiler/rustc_target/src/spec/nvptx64_nvidia_cuda.rs

@@ -14,6 +14,7 @@ pub fn target() -> Target {
             linker_flavor: LinkerFlavor::PtxLinker,
             // The linker can be installed from `crates.io`.
             linker: Some("rust-ptx-linker".to_string()),
+            linker_is_gnu: false,
 
             // With `ptx-linker` approach, it can be later overridden via link flags.
             cpu: "sm_30".to_string(),

compiler/rustc_target/src/spec/openbsd_base.rs

@@ -6,7 +6,6 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         families: vec!["unix".to_string()],
-        linker_is_gnu: true,
         has_rpath: true,
         abi_return_struct_as_int: true,
         position_independent_executables: true,

compiler/rustc_target/src/spec/redox_base.rs

@@ -7,7 +7,6 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         families: vec!["unix".to_string()],
-        linker_is_gnu: true,
         has_rpath: true,
         position_independent_executables: true,
         relro_level: RelroLevel::Full,

compiler/rustc_target/src/spec/solaris_base.rs

@@ -8,6 +8,7 @@ pub fn opts() -> TargetOptions {
         has_rpath: true,
         families: vec!["unix".to_string()],
         is_like_solaris: true,
+        linker_is_gnu: false,
         limit_rdylib_exports: false, // Linker doesn't support this
         eh_frame_header: false,
 

compiler/rustc_target/src/spec/thumbv4t_none_eabi.rs

@@ -28,7 +28,6 @@ pub fn target() -> Target {
         options: TargetOptions {
             linker_flavor: LinkerFlavor::Ld,
             linker: Some("arm-none-eabi-ld".to_string()),
-            linker_is_gnu: true,
 
             // extra args passed to the external assembler (assuming `arm-none-eabi-as`):
             // * activate t32/a32 interworking

compiler/rustc_target/src/spec/vxworks_base.rs

@@ -10,7 +10,6 @@ pub fn opts() -> TargetOptions {
         dynamic_linking: true,
         executables: true,
         families: vec!["unix".to_string()],
-        linker_is_gnu: true,
         has_rpath: true,
         has_elf_tls: true,
         crt_static_default: true,

compiler/rustc_target/src/spec/wasm32_unknown_emscripten.rs

@@ -34,7 +34,6 @@ pub fn target() -> Target {
         // functionality, and a .wasm file.
         exe_suffix: ".js".to_string(),
         linker: None,
-        linker_is_gnu: true,
         is_like_emscripten: true,
         panic_strategy: PanicStrategy::Unwind,
         post_link_args,

compiler/rustc_target/src/spec/windows_gnu_base.rs

@@ -66,7 +66,6 @@ pub fn opts() -> TargetOptions {
         // FIXME(#13846) this should be enabled for windows
         function_sections: false,
         linker: Some("gcc".to_string()),
-        linker_is_gnu: true,
         dynamic_linking: true,
         executables: true,
         dll_prefix: String::new(),

compiler/rustc_target/src/spec/x86_64_fortanix_unknown_sgx.rs

@@ -57,7 +57,6 @@ pub fn target() -> Target {
         vendor: "fortanix".into(),
         linker_flavor: LinkerFlavor::Lld(LldFlavor::Ld),
         executables: true,
-        linker_is_gnu: true,
         linker: Some("rust-lld".to_owned()),
         max_atomic_width: Some(64),
         cpu: "x86-64".into(),