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/testing.go b/cc/testing.go
index 18cc83f..417ea4a 100644
--- a/cc/testing.go
+++ b/cc/testing.go
@@ -265,6 +265,7 @@
 	ctx.RegisterModuleType("toolchain_library", ToolchainLibraryFactory)
 	ctx.RegisterModuleType("llndk_library", LlndkLibraryFactory)
 	ctx.RegisterModuleType("llndk_headers", llndkHeadersFactory)
+	ctx.RegisterModuleType("ndk_library", NdkLibraryFactory)
 	ctx.RegisterModuleType("vendor_public_library", vendorPublicLibraryFactory)
 	ctx.RegisterModuleType("cc_object", ObjectFactory)
 	ctx.RegisterModuleType("filegroup", android.FileGroupFactory)