build: Never explicitly link clang_rt.builtins

https://chromium-review.googlesource.com/c/chromium/src/+/5723176

src/build/config/clang/BUILD.gn

@@ -257,7 +257,10 @@ template("clang_lib") {
 
 # Adds a dependency on the Clang runtime library clang_rt.builtins.
 clang_lib("compiler_builtins") {
-  if (is_mac) {
+  if (true) {
+    # NaiveProxy doesn't use Rust and never links clang_rt.builtins.
+    # Don't define libname which makes this target do nothing.
+  } else if (is_mac) {
     libname = "osx"
   } else if (is_ios) {
     if (target_platform == "iphoneos") {