Enable YogaKit for tvOS

Summary:
This is used in a stack where I'm using YogaKit on tvOS. fb_apple_library needs `sdks = ` to get buck to do its thing for tvOS.

This seems like it should be OK since apple_library is a nop on non apple platforms (which makes sense since this is ObjC only) - I think that makes sense anyway?

Reviewed By: emilsjolander

Differential Revision: D5080261

fbshipit-source-id: f08d7e6d2599b9af25fb964ade485aef552f306b

YogaKit/BUCK

@@ -36,6 +36,7 @@ apple_library(
         "$SDKROOT/System/Library/Frameworks/Foundation.framework",
         "$SDKROOT/System/Library/Frameworks/UIKit.framework",
     ],
+    sdks = (IOS, APPLETVOS),
     visibility = ["PUBLIC"],
     deps = [
         yoga_dep(":yoga"),