Add preparers for xml

Bug: 181070625
Test: m nothing
Change-Id: I150889a025e1c23eebe1e2764b07fdbd2babef49
diff --git a/xml/xml.go b/xml/xml.go
index 8810ae4..c281078 100644
--- a/xml/xml.go
+++ b/xml/xml.go
@@ -53,10 +53,14 @@
 )
 
 func init() {
-	android.RegisterModuleType("prebuilt_etc_xml", PrebuiltEtcXmlFactory)
+	registerXmlBuildComponents(android.InitRegistrationContext)
 	pctx.HostBinToolVariable("XmlLintCmd", "xmllint")
 }
 
+func registerXmlBuildComponents(ctx android.RegistrationContext) {
+	ctx.RegisterModuleType("prebuilt_etc_xml", PrebuiltEtcXmlFactory)
+}
+
 type prebuiltEtcXmlProperties struct {
 	// Optional DTD that will be used to validate the xml file.
 	Schema *string `android:"path"`