Make PrebuiltEtcHostFactory public.

Bug: 122332220
Test: prebuilt_etc_test.go + manual builds
Change-Id: Ia2f882f0d18f3f06f396b2bf3f3052d27c6ab96d
diff --git a/android/prebuilt_etc.go b/android/prebuilt_etc.go
index 33647d7..8af08c1 100644
--- a/android/prebuilt_etc.go
+++ b/android/prebuilt_etc.go
@@ -25,7 +25,7 @@
 
 func init() {
 	RegisterModuleType("prebuilt_etc", PrebuiltEtcFactory)
-	RegisterModuleType("prebuilt_etc_host", prebuiltEtcHostFactory)
+	RegisterModuleType("prebuilt_etc_host", PrebuiltEtcHostFactory)
 
 	PreDepsMutators(func(ctx RegisterMutatorsContext) {
 		ctx.BottomUp("prebuilt_etc", prebuiltEtcMutator).Parallel()
@@ -182,7 +182,7 @@
 	return module
 }
 
-func prebuiltEtcHostFactory() Module {
+func PrebuiltEtcHostFactory() Module {
 	module := &PrebuiltEtc{}
 	InitPrebuiltEtcModule(module)
 	// This module is host-only