Fix native build

Summary:
- Fix OSS build regarding is_apple_platform
- Update buck
- Drop 32bit build for Apple target

Reviewed By: ttsugriy

Differential Revision: D7032331

fbshipit-source-id: bb6a24bd404a107729a30b5ac4b419c238f7d42e

yoga_defs.bzl

@@ -105,3 +105,8 @@ def prebuilt_cxx_library(*args, **kwargs):
 _original_prebuilt_jar = prebuilt_jar
 def prebuilt_jar(*args, **kwargs):
   _original_prebuilt_jar(*args, **kwargs)
+
+
+def is_apple_platform():
+  return True
+