Add Yoga JNI bindings to libcoldstart

Summary:
Yoga's JNI bindings are usually loaded during class loading, and can stall the UI thread.

Here, we try to mitigate the problem by adding the bindings to libcoldstart.

Reviewed By: michalgr

Differential Revision: D12956818

fbshipit-source-id: 9dda5cb6d26c2bae64606bc2d7c98ab8f7c05a30

java/BUCK

@@ -10,6 +10,7 @@ yoga_cxx_library(
     srcs = glob(["jni/*.cpp"]),
     headers = glob(["jni/*.h"]),
     header_namespace = "",
+    allow_jni_merging = True,
     compiler_flags = [
         "-fno-omit-frame-pointer",
         "-fexceptions",