Support apps attribute in apex_defaults

Adding overridableProperties to apex_defaults as well.

Bug: 146217017
Test: m
Change-Id: I51182fec25ee589fea4006164c4dd69acc5ba67d
diff --git a/apex/apex.go b/apex/apex.go
index be86d80..727b2f7 100644
--- a/apex/apex.go
+++ b/apex/apex.go
@@ -483,9 +483,11 @@
 
 	properties            apexBundleProperties
 	targetProperties      apexTargetBundleProperties
-	vndkProperties        apexVndkProperties
 	overridableProperties overridableProperties
 
+	// specific to apex_vndk modules
+	vndkProperties apexVndkProperties
+
 	bundleModuleFile android.WritablePath
 	outputFile       android.WritablePath
 	installDir       android.InstallPath
@@ -1273,6 +1275,7 @@
 	module.AddProperties(
 		&apexBundleProperties{},
 		&apexTargetBundleProperties{},
+		&overridableProperties{},
 	)
 
 	android.InitDefaultsModule(module)