Fix ScopeReflectionTestIsBuiltin emsdk 4.0.18

Author: mcbarton

unittests/CppInterOp/ScopeReflectionTest.cpp

@@ -220,7 +220,7 @@ TYPED_TEST(CppInterOpTest, ScopeReflectionTestIsBuiltin) {
   //  "int", "unsigned int", "long", "unsigned long", "long long", "unsigned long long",
   //  "float", "double", "long double", "void"}
 
-  std::vector<const char*> interpreter_args = { "-include", "new" };
+  std::vector<const char*> interpreter_args = { "-include", "new", "-Xclang", "-iwithsysroot/include/compat" };
 
   TestFixture::CreateInterpreter(interpreter_args);
   ASTContext &C = Interp->getCI()->getASTContext();