Expand ClangExtraExternalCflags to non-Google vendor projects

Some of the warnings are too common to fix/opt-out for non-Google
projects.

Also in the change, minor clean up of duplicated code.

Test: presubmit
Bug: 139945549
Change-Id: Ic176ef1f17133405851a79592b6bef5ccb403bd9

cc/compiler_test.go

@@ -0,0 +1,43 @@
+// Copyright 2019 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package cc
+
+import (
+	"testing"
+)
+
+func TestIsThirdParty(t *testing.T) {
+	shouldFail := []string{
+		"external/foo/",
+		"vendor/bar/",
+		"hardware/underwater_jaguar/",
+	}
+	shouldPass := []string{
+		"vendor/google/cts/",
+		"hardware/google/pixel",
+		"hardware/interfaces/camera",
+		"hardware/ril/supa_ril",
+	}
+	for _, path := range shouldFail {
+		if !isThirdParty(path) {
+			t.Errorf("Expected %s to be considered third party", path)
+		}
+	}
+	for _, path := range shouldPass {
+		if isThirdParty(path) {
+			t.Errorf("Expected %s to *not* be considered third party", path)
+		}
+	}
+}