Use tidyExternalVendor for external/googletest

* Do not run expensive clang-analyzer-* checks with googletest/*,
  which should be checked upstream.

Test: make WITH_TIDY=1 CLANG_ANALYZER_CHECKS=1
Bug: 198098397
Change-Id: Ic801ffa802b42d4d55ae89553073c926f9eaa351
diff --git a/cc/config/tidy.go b/cc/config/tidy.go
index cf13503..8682502 100644
--- a/cc/config/tidy.go
+++ b/cc/config/tidy.go
@@ -115,6 +115,7 @@
 	{"external/", tidyExternalVendor},
 	{"external/google", tidyDefault},
 	{"external/webrtc", tidyDefault},
+	{"external/googletest/", tidyExternalVendor},
 	{"frameworks/compile/mclinker/", tidyExternalVendor},
 	{"hardware/qcom", tidyExternalVendor},
 	{"vendor/", tidyExternalVendor},
@@ -133,6 +134,7 @@
 }
 
 func TidyChecksForDir(dir string) string {
+	dir = dir + "/"
 	for _, pathCheck := range reversedDefaultLocalTidyChecks {
 		if strings.HasPrefix(dir, pathCheck.PathPrefix) {
 			return pathCheck.Checks