f2fs: Re-add the Darwin hax
f2fs: Re-add the Darwin hax

Change-Id: Ibd65081c350f362d3484d9865c651837371bf870

AOSP-YU/platform_external_f2fs-tools,YUPlayGodDev/platform_external_f2fs-tools,YUPlayGodDev/platform_external_f2fs-tools,AOSP-YU/platform_external_f2fs-tools