Implement cc_object vendor snapshot

cc_object modules are also necessary for vendor snapshot.

Bug: 157106227
Test: m vendor-snapshot
Change-Id: Idf4fd37a26f6f712f3cbab43133622f9f9bd9372
Merged-In: Idf4fd37a26f6f712f3cbab43133622f9f9bd9372
(cherry picked from commit 502679e061)

cc/prebuilt.go

@@ -291,6 +291,10 @@ func (p *prebuiltObjectLinker) link(ctx ModuleContext,
 	return nil
 }
 
+func (p *prebuiltObjectLinker) object() bool {
+	return true
+}
+
 func newPrebuiltObject() *Module {
 	module := newObject()
 	prebuilt := &prebuiltObjectLinker{