Add overrides support for snapshots

Overrides properties will now be captured in json flag files, which will
be copied to installed vendor snapshot modules.

Bug: 216567575
Test: soong test && manual install
Change-Id: Ife5e84b126e798fba7802b9cff000c9197756cb9

cc/library.go

@@ -2231,6 +2231,12 @@ func (library *libraryDecorator) getAPIListCoverageXMLPath() android.ModuleOutPa
 	return library.apiListCoverageXmlPath
 }
 
+func (library *libraryDecorator) overriddenModules() []string {
+	return library.Properties.Overrides
+}
+
+var _ overridable = (*libraryDecorator)(nil)
+
 var versioningMacroNamesListKey = android.NewOnceKey("versioningMacroNamesList")
 
 // versioningMacroNamesList returns a singleton map, where keys are "version macro names",