Windows mingw targets use gcc as the linker so the target spec should also indicate linker_is_gnu.

compiler/rustc_target/src/spec/windows_gnu_base.rs

@@ -66,6 +66,7 @@ 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(),