Switch PackageContext functions to take a ctx

So that the Path and similar functions can be used directly, without
manually adding something like configErrorWrapper (it just uses it all
the time now).

Test: out/soong/build.ninja is identical
Change-Id: I8cb524b09a84d0b8357d7c3501c71270af411e17

java/config/error_prone.go

@@ -27,8 +27,8 @@ var (
 
 // Wrapper that grabs value of val late so it can be initialized by a later module's init function
 func errorProneVar(name string, val *string) {
-	pctx.VariableFunc(name, func(config android.Config) (string, error) {
-		return *val, nil
+	pctx.VariableFunc(name, func(android.PackageVarContext) string {
+		return *val
 	})
 }