Dedup java genrule module type registration

Test: m checkbuild
Bug: 146540677
Change-Id: I17f24fe145b4bb453e82aabaecc9c251f2b9769b
diff --git a/java/genrule.go b/java/genrule.go
index 25494ec..e0a9c8f 100644
--- a/java/genrule.go
+++ b/java/genrule.go
@@ -20,8 +20,12 @@
 )
 
 func init() {
-	android.RegisterModuleType("java_genrule", genRuleFactory)
-	android.RegisterModuleType("java_genrule_host", genRuleFactoryHost)
+	RegisterGenRuleBuildComponents(android.InitRegistrationContext)
+}
+
+func RegisterGenRuleBuildComponents(ctx android.RegistrationContext) {
+	ctx.RegisterModuleType("java_genrule", genRuleFactory)
+	ctx.RegisterModuleType("java_genrule_host", genRuleFactoryHost)
 }
 
 // java_genrule is a genrule that can depend on other java_* objects.