Skipp GCC backend-specific test if current backend is already gcc

Author: GuillaumeGomez

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

@@ -3744,6 +3744,15 @@ impl Step for CodegenGCC {
             return;
         }
 
+        // It we were running with GCC backend tests, no need to run these tests.
+        if let Some(codegen_backend) = run.builder.config.cmd.test_codegen_backend() {
+            if codegen_backend.is_gcc() {
+                return;
+            }
+        } else if run.builder.config.default_codegen_backend(compiler.host).is_gcc() {
+            return;
+        }
+
         if builder.download_rustc() {
             builder.info("CI rustc uses the default codegen backend. skipping");
             return;