Improve commenting for cc/builer.go, and kill dead code

Test: m nothing
Change-Id: I836c717d3243e901257120be71246e419de4d28e
diff --git a/cc/compiler.go b/cc/compiler.go
index 04ed80d..f71dcca 100644
--- a/cc/compiler.go
+++ b/cc/compiler.go
@@ -649,7 +649,7 @@
 func compileObjs(ctx android.ModuleContext, flags builderFlags,
 	subdir string, srcFiles, pathDeps android.Paths, cFlagsDeps android.Paths) Objects {
 
-	return TransformSourceToObj(ctx, subdir, srcFiles, flags, pathDeps, cFlagsDeps)
+	return transformSourceToObj(ctx, subdir, srcFiles, flags, pathDeps, cFlagsDeps)
 }
 
 var thirdPartyDirPrefixExceptions = []*regexp.Regexp{