Only use -fgnuc-version=4.2.1 when parsing C headers with Clang

Author: emillaine

src/driver/driver.cpp

@@ -535,7 +535,6 @@ static int buildPackage(llvm::StringRef packageRoot, const char* argv0) {
 }
 
 static void addPlatformCompileOptions() {
-    cflags.push_back("-fgnuc-version=4.2.1");
 #ifdef _WIN32
     defines.push_back("Windows");
     cflags.push_back("-fms-extensions");

src/sema/c-import.cpp

@@ -359,6 +359,7 @@ bool cx::importCHeader(SourceFile& importer, llvm::StringRef headerName, const C
     ci.createDiagnostics(*llvm::vfs::getRealFileSystem(), diagClient);
 
     auto args = map(options.cflags, [](auto& cflag) { return cflag.c_str(); });
+    args.push_back("-fgnuc-version=4.2.1");
     clang::CompilerInvocation::CreateFromArgs(ci.getInvocation(), args, ci.getDiagnostics());
 
     auto pto = std::make_shared<clang::TargetOptions>();