update bootstrap mcp510 handling

now that it's been stabilized, beta and stage1 need to use different
flags (-C vs -Z)

Author: lqd

src/bootstrap/src/core/build_steps/test.rs

@@ -262,7 +262,13 @@ impl Step for Cargotest {
             .args(builder.config.test_args())
             .env("RUSTC", builder.rustc(compiler))
             .env("RUSTDOC", builder.rustdoc(compiler));
-        add_rustdoc_cargo_linker_args(&mut cmd, builder, compiler.host, LldThreads::No);
+        add_rustdoc_cargo_linker_args(
+            &mut cmd,
+            builder,
+            compiler.host,
+            LldThreads::No,
+            compiler.stage,
+        );
         cmd.delay_failure().run(builder);
     }
 }
@@ -857,7 +863,7 @@ impl Step for RustdocTheme {
             .env("CFG_RELEASE_CHANNEL", &builder.config.channel)
             .env("RUSTDOC_REAL", builder.rustdoc(self.compiler))
             .env("RUSTC_BOOTSTRAP", "1");
-        cmd.args(linker_args(builder, self.compiler.host, LldThreads::No));
+        cmd.args(linker_args(builder, self.compiler.host, LldThreads::No, self.compiler.stage));
 
         cmd.delay_failure().run(builder);
     }
@@ -1033,7 +1039,13 @@ impl Step for RustdocGUI {
         cmd.env("RUSTDOC", builder.rustdoc(self.compiler))
             .env("RUSTC", builder.rustc(self.compiler));
 
-        add_rustdoc_cargo_linker_args(&mut cmd, builder, self.compiler.host, LldThreads::No);
+        add_rustdoc_cargo_linker_args(
+            &mut cmd,
+            builder,
+            self.compiler.host,
+            LldThreads::No,
+            self.compiler.stage,
+        );
 
         for path in &builder.paths {
             if let Some(p) = helpers::is_valid_test_suite_arg(path, "tests/rustdoc-gui", builder) {
@@ -1802,7 +1814,7 @@ NOTE: if you're sure you want to do this, please open an issue as to why. In the
         }
 
         let mut hostflags = flags.clone();
-        hostflags.extend(linker_flags(builder, compiler.host, LldThreads::No));
+        hostflags.extend(linker_flags(builder, compiler.host, LldThreads::No, compiler.stage));
 
         let mut targetflags = flags;
 

src/bootstrap/src/core/builder/cargo.rs

@@ -115,7 +115,7 @@ impl Cargo {
             // No need to configure the target linker for these command types.
             Kind::Clean | Kind::Check | Kind::Suggest | Kind::Format | Kind::Setup => {}
             _ => {
-                cargo.configure_linker(builder);
+                cargo.configure_linker(builder, mode);
             }
         }
 
@@ -206,7 +206,7 @@ impl Cargo {
 
     // FIXME(onur-ozkan): Add coverage to make sure modifications to this function
     // doesn't cause cache invalidations (e.g., #130108).
-    fn configure_linker(&mut self, builder: &Builder<'_>) -> &mut Cargo {
+    fn configure_linker(&mut self, builder: &Builder<'_>, mode: Mode) -> &mut Cargo {
         let target = self.target;
         let compiler = self.compiler;
 
@@ -261,7 +261,15 @@ impl Cargo {
             }
         }
 
-        for arg in linker_args(builder, compiler.host, LldThreads::Yes) {
+        // When determining flags for the host (build scripts/proc macros),
+        // we use the snapshot compiler when building `Mode::Std` tools, and
+        // the current compiler when building anything else.
+        // We need to determine the current stage here to pass proper linker args (e.g. -C vs -Z)
+        // to the compiler used to compile build scripts.
+        // This should stay synchronized with the [cargo] function.
+        let host_stage = if mode == Mode::Std { 0 } else { compiler.stage };
+
+        for arg in linker_args(builder, compiler.host, LldThreads::Yes, host_stage) {
             self.hostflags.arg(&arg);
         }
 
@@ -271,10 +279,10 @@ impl Cargo {
         }
         // We want to set -Clinker using Cargo, therefore we only call `linker_flags` and not
         // `linker_args` here.
-        for flag in linker_flags(builder, target, LldThreads::Yes) {
+        for flag in linker_flags(builder, target, LldThreads::Yes, compiler.stage) {
             self.rustflags.arg(&flag);
         }
-        for arg in linker_args(builder, target, LldThreads::Yes) {
+        for arg in linker_args(builder, target, LldThreads::Yes, compiler.stage) {
             self.rustdocflags.arg(&arg);
         }
 

src/bootstrap/src/core/builder/mod.rs

@@ -1481,7 +1481,7 @@ impl<'a> Builder<'a> {
             cmd.arg("-Dwarnings");
         }
         cmd.arg("-Znormalize-docs");
-        cmd.args(linker_args(self, compiler.host, LldThreads::Yes));
+        cmd.args(linker_args(self, compiler.host, LldThreads::Yes, compiler.stage));
         cmd
     }
 

src/bootstrap/src/utils/helpers.rs

@@ -465,8 +465,9 @@ pub fn linker_args(
     builder: &Builder<'_>,
     target: TargetSelection,
     lld_threads: LldThreads,
+    stage: u32,
 ) -> Vec<String> {
-    let mut args = linker_flags(builder, target, lld_threads);
+    let mut args = linker_flags(builder, target, lld_threads, stage);
 
     if let Some(linker) = builder.linker(target) {
         args.push(format!("-Clinker={}", linker.display()));
@@ -481,19 +482,30 @@ pub fn linker_flags(
     builder: &Builder<'_>,
     target: TargetSelection,
     lld_threads: LldThreads,
+    stage: u32,
 ) -> Vec<String> {
     let mut args = vec![];
     if !builder.is_lld_direct_linker(target) && builder.config.lld_mode.is_used() {
         match builder.config.lld_mode {
             LldMode::External => {
-                args.push("-Zlinker-features=+lld".to_string());
-                // FIXME(kobzol): remove this flag once MCP510 gets stabilized
+                // cfg(bootstrap) - remove the stage 0 check after updating the bootstrap compiler:
+                // `-Clinker-features` has been stabilized.
+                if stage == 0 {
+                    args.push("-Zlinker-features=+lld".to_string());
+                } else {
+                    args.push("-Clinker-features=+lld".to_string());
+                }
                 args.push("-Zunstable-options".to_string());
             }
             LldMode::SelfContained => {
-                args.push("-Zlinker-features=+lld".to_string());
+                // cfg(bootstrap) - remove the stage 0 check after updating the bootstrap compiler:
+                // `-Clinker-features` has been stabilized.
+                if stage == 0 {
+                    args.push("-Zlinker-features=+lld".to_string());
+                } else {
+                    args.push("-Clinker-features=+lld".to_string());
+                }
                 args.push("-Clink-self-contained=+linker".to_string());
-                // FIXME(kobzol): remove this flag once MCP510 gets stabilized
                 args.push("-Zunstable-options".to_string());
             }
             LldMode::Unused => unreachable!(),
@@ -514,8 +526,9 @@ pub fn add_rustdoc_cargo_linker_args(
     builder: &Builder<'_>,
     target: TargetSelection,
     lld_threads: LldThreads,
+    stage: u32,
 ) {
-    let args = linker_args(builder, target, lld_threads);
+    let args = linker_args(builder, target, lld_threads, stage);
     let mut flags = cmd
         .get_envs()
         .find_map(|(k, v)| if k == OsStr::new("RUSTDOCFLAGS") { v } else { None })