Make Config.ProductVariables private

All access to these should be going through the methods on Config /
DeviceConfig.

Bug: 76168832
Test: m blueprint_tools
Change-Id: I47512dd58fb1a1a3f25838a9b1adaed2c41af8d3
diff --git a/android/androidmk.go b/android/androidmk.go
index ebed05f..a60520f 100644
--- a/android/androidmk.go
+++ b/android/androidmk.go
@@ -72,7 +72,7 @@
 
 	sort.Sort(AndroidModulesByName{androidMkModulesList, ctx})
 
-	transMk := PathForOutput(ctx, "Android"+String(ctx.Config().ProductVariables.Make_suffix)+".mk")
+	transMk := PathForOutput(ctx, "Android"+String(ctx.Config().productVariables.Make_suffix)+".mk")
 	if ctx.Failed() {
 		return
 	}