Simple refactoring of prefix related functions.

Rename the two prefix-in-list funcs so that their usages are clearer.
Also find and replace all the code that essentially does either.

This introduces additional loops in some places, but I think the added
readability and simplicity outweighs the performance degradation, which
should be negligible anyway.

Test: m nothing
Test: TreeHugger
Change-Id: I37e2276ca0c815105ed0031f23c0b1264b480e4f

cc/cflag_artifacts.go

@@ -41,12 +41,7 @@ type cflagArtifactsText struct {
 // filter.
 func allowedDir(subdir string) bool {
 	subdir += "/"
-	for _, prefix := range TrackedCFlagsDir {
-		if strings.HasPrefix(subdir, prefix) {
-			return true
-		}
-	}
-	return false
+	return android.HasAnyPrefix(subdir, TrackedCFlagsDir)
 }
 
 func (s *cflagArtifactsText) genFlagFilename(flag string) string {