Prebuilt is enabled even if the source one is not.

This fix a bug in a recent android_app_import-related change
(I8215aa1a6dad74b503eaa1169a64f8c30dda287c) where it uses an incorrect
module reference, and so disables a prebuilt module if its source-based
counterpart is disabled.

Test: app_test.go
Bug: 152343232
Change-Id: Ic7f5ca40be58f06e44b5ec4945caf209ef2dae96

android/prebuilt.go

@@ -178,7 +178,7 @@ func InitSingleSourcePrebuiltModule(module PrebuiltInterface, srcProps interface
 	srcPropertyName := proptools.PropertyNameForField(srcField)
 
 	srcsSupplier := func(ctx BaseModuleContext) []string {
-		if !ctx.Module().Enabled() {
+		if !module.Enabled() {
 			return nil
 		}
 		value := srcPropsValue.FieldByIndex(srcFieldIndex)