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/cc.go b/cc/cc.go
index e80e2a2..03ab4e4 100644
--- a/cc/cc.go
+++ b/cc/cc.go
@@ -38,7 +38,7 @@
 	android.PreDepsMutators(func(ctx android.RegisterMutatorsContext) {
 		ctx.BottomUp("vndk", VndkMutator).Parallel()
 		ctx.BottomUp("link", LinkageMutator).Parallel()
-		ctx.BottomUp("ndk_api", ndkApiMutator).Parallel()
+		ctx.BottomUp("ndk_api", NdkApiMutator).Parallel()
 		ctx.BottomUp("test_per_src", TestPerSrcMutator).Parallel()
 		ctx.BottomUp("version", VersionMutator).Parallel()
 		ctx.BottomUp("begin", BeginMutator).Parallel()