Turns out we can eliminate this setting and just turn on ARC for ARM64_32.
<rdar://problem/35181521>
Created attachment 324882 [details] Patch
Comment on attachment 324882 [details] Patch r=me
Comment on attachment 324882 [details] Patch Clearing flags on attachment: 324882 Committed r223980: <https://trac.webkit.org/changeset/223980>
All reviewed patches have been landed. Closing bug.