Expose some factories for aidl_test.go

Because aidl_interface depends on some ndk modules, their factories are
exposed so that aidl_test.go can use them.

Bug: n/a
Test: m
Change-Id: I98d282cc77310d5896a7abaf3936456a14d56ccf
diff --git a/cc/ndk_sysroot.go b/cc/ndk_sysroot.go
index f6de4ef..56fd54b 100644
--- a/cc/ndk_sysroot.go
+++ b/cc/ndk_sysroot.go
@@ -58,7 +58,7 @@
 
 func init() {
 	android.RegisterModuleType("ndk_headers", ndkHeadersFactory)
-	android.RegisterModuleType("ndk_library", ndkLibraryFactory)
+	android.RegisterModuleType("ndk_library", NdkLibraryFactory)
 	android.RegisterModuleType("versioned_ndk_headers", versionedNdkHeadersFactory)
 	android.RegisterModuleType("preprocessed_ndk_headers", preprocessedNdkHeadersFactory)
 	android.RegisterSingletonType("ndk", NdkSingleton)