Summary:
`xplat` targets add different deps based on what platform the target is being built for.
for anything using `fb_xplat`, we can put all ios supermodules in `fbobjc_labels` and all android sms in `fbandroid_labels`
There's some weirdness with python targets like `thrift_gen` in `/xplat/mobileconfig/tools/generator/gen-py/BUCK` that don't have platform-specific labels because the except_for list for `fbandroid` doesn't need the `fbsource//` prefix (see changes in `/ios/isolation/infra.mobileconfig.sm`)
Changelog: [Internal]
Reviewed By: shergin, joshleibsly
Differential Revision: D17884952
fbshipit-source-id: e245364cf515b75682990094d24f789d53b1f3f5
Janette Cheng
10cc834567