ignore linker errors on all platforms

Author: jyn514

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

@@ -3611,6 +3611,8 @@ impl Step for CodegenGCC {
         let mut cargo = build_cargo();
 
         cargo
+            // cg_gcc's build system ignores RUSTFLAGS. pass some flags through CG_RUSTFLAGS instead.
+            .env("CG_RUSTFLAGS", "-Alinker-messages")
             .arg("--")
             .arg("test")
             .arg("--use-system-gcc")

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

@@ -270,6 +270,12 @@ impl Cargo {
             self.rustflags.arg("-Clink-arg=-gz");
         }
 
+        // Ignore linker warnings for now. These are complicated to fix and don't affect the build.
+        // cfg(bootstrap)
+        if compiler.stage != 0 {
+            self.rustflags.arg("-Alinker-messages");
+        }
+
         // Throughout the build Cargo can execute a number of build scripts
         // compiling C/C++ code and we need to pass compilers, archivers, flags, etc
         // obtained previously to those build scripts.