Change default DEFAULT_TIDY_HEADER_DIRS to empty

* Default -header-filter will now contain only module directory.
  * In a clean build of aosp_x86_64-eng, this change can reduce
    the number of (duplicated) clang-tidy warnings by 77% or more.
* When compiled with WITH_TIDY=1, if DEFAULT_TIDY_HEADER_DIRS is
  not set, warnings from a header file will be shown only if
  the file is in a module's (sub)directory.
* Set DEFAULT_TIDY_HEADER_DIRS="bionic/|bootable/|build/|cts/|\
  dalvik/|developers/|development/|frameworks/|\
  libcore/|libnativehelper/|system/"
  will get before this change's -header-filter.
* Fix a bug: Default header-filter was not added when
  tidy_flags was defined in a module.
  With this fix, some incorrectly hidden header file tidy warnings
  will now show up.

Bug: 179530304
Test: make with WITH_TIDY=1 and various setting of DEFAULT_TIDY_HEADER_DIRS
Change-Id: Ia0c05349908a730862dae36be9a2dbe4f44fb6da
diff --git a/android/util.go b/android/util.go
index 0f940fa..506f8f7 100644
--- a/android/util.go
+++ b/android/util.go
@@ -137,6 +137,16 @@
 	return false
 }
 
+// Returns true if any string in the given list has the given substring.
+func SubstringInList(list []string, substr string) bool {
+	for _, s := range list {
+		if strings.Contains(s, substr) {
+			return true
+		}
+	}
+	return false
+}
+
 // Returns true if any string in the given list has the given prefix.
 func PrefixInList(list []string, prefix string) bool {
 	for _, s := range list {