make optimized-compiler-builtins target configurable

Signed-off-by: onur-ozkan <work@onurozkan.dev>

src/bootstrap/src/core/build_steps/compile.rs

@@ -469,7 +469,7 @@ pub fn std_cargo(builder: &Builder<'_>, target: TargetSelection, stage: u32, car
     // If `compiler-rt` is available ensure that the `c` feature of the
     // `compiler-builtins` crate is enabled and it's configured to learn where
     // `compiler-rt` is located.
-    let compiler_builtins_c_feature = if builder.config.optimized_compiler_builtins {
+    let compiler_builtins_c_feature = if builder.config.optimized_compiler_builtins(target) {
         // NOTE: this interacts strangely with `llvm-has-rust-patches`. In that case, we enforce `submodules = false`, so this is a no-op.
         // But, the user could still decide to manually use an in-tree submodule.
         //

src/bootstrap/src/core/config/config.rs

@@ -634,6 +634,7 @@ pub struct Target {
     pub runner: Option<String>,
     pub no_std: bool,
     pub codegen_backends: Option<Vec<String>>,
+    pub optimized_compiler_builtins: Option<bool>,
 }
 
 impl Target {
@@ -1219,6 +1220,7 @@ define_config! {
         no_std: Option<bool> = "no-std",
         codegen_backends: Option<Vec<String>> = "codegen-backends",
         runner: Option<String> = "runner",
+        optimized_compiler_builtins: Option<bool> = "optimized-compiler-builtins",
     }
 }
 
@@ -2096,6 +2098,7 @@ impl Config {
                 target.sanitizers = cfg.sanitizers;
                 target.profiler = cfg.profiler;
                 target.rpath = cfg.rpath;
+                target.optimized_compiler_builtins = cfg.optimized_compiler_builtins;
 
                 if let Some(ref backends) = cfg.codegen_backends {
                     let available_backends = ["llvm", "cranelift", "gcc"];
@@ -2609,6 +2612,13 @@ impl Config {
         self.target_config.get(&target).and_then(|t| t.rpath).unwrap_or(self.rust_rpath)
     }
 
+    pub fn optimized_compiler_builtins(&self, target: TargetSelection) -> bool {
+        self.target_config
+            .get(&target)
+            .and_then(|t| t.optimized_compiler_builtins)
+            .unwrap_or(self.optimized_compiler_builtins)
+    }
+
     pub fn llvm_enabled(&self, target: TargetSelection) -> bool {
         self.codegen_backends(target).contains(&"llvm".to_owned())
     }