[cc] Cleanup unused function

Test: TH
Change-Id: I7c7fd1ada1303e8006b27923f124c836a4776d8b
diff --git a/cc/config/global.go b/cc/config/global.go
index d458311..24e10a4 100644
--- a/cc/config/global.go
+++ b/cc/config/global.go
@@ -294,12 +294,3 @@
 }
 
 var HostPrebuiltTag = pctx.VariableConfigMethod("HostPrebuiltTag", android.Config.PrebuiltOS)
-
-func envOverrideFunc(envVar, defaultVal string) func(ctx android.PackageVarContext) string {
-	return func(ctx android.PackageVarContext) string {
-		if override := ctx.Config().Getenv(envVar); override != "" {
-			return override
-		}
-		return defaultVal
-	}
-}