Summary:
The source of truth has already moved, so now we just need to fix references
This diff is mostly the result of running:
```
$ tools/mobile-unification/loadmod --fixup xplat/configurations/buck/apple/flag_defs.bzl tools/build_defs/apple/
```
Then I committed with `hg commit -I xplat/`
The controller you requested could not be found.
Differential Revision: D9772194
fbshipit-source-id: 93d23ae8e1c62440c7876cad965d963bde960db9
686ff70d96