Build iOS fat static library for Unity and Xamarin
Build iOS fat static library for Unity and Xamarin

Summary:
$ buck build //csharp:yoganet-ios
    $ buck targets --show-output //csharp:yoganet-ios
    //csharp:yoganet-ios buck-out/gen/csharp/yoganet-ios/libyoga.a

    $ lipo -info buck-out/gen/csharp/yoganet-ios/libyoga.a
    Architectures in the fat file: buck-out/gen/csharp/yoganet-ios/libyoga.a are: armv7 x86_64 arm64

    $ nm buck-out/gen/csharp/yoganet-ios/libyoga.a|grep -e 'T _YGNodeNew' -e 'ygNode' -e 'T _YGInteropSetLogger'
    0000000000000000 T _YGNodeNew
    0000000000001070 t -[UIView(Yoga) ygNode]
    0000000000000000 T _YGInteropSetLogger
Closes https://github.com/facebook/yoga/pull/286

Reviewed By: emilsjolander

Differential Revision: D4338919

Pulled By: splhack

fbshipit-source-id: 7acfdfa0dc4d152d7bfe92161efdeb9f161f70e6

rmarinho/yoga,rmarinho/yoga,facebook/css-layout,facebook/yoga,rmarinho/yoga,yihuang/css-layout,rmarinho/yoga,rmarinho/yoga,facebook/yoga,facebook/css-layout,facebook/css-layout,yihuang/css-layout,rmarinho/yoga,yihuang/css-layout,rmarinho/yoga,rmarinho/yoga,yihuang/css-layout,facebook/yoga,facebook/css-layout,yihuang/css-layout,facebook/css-layout,rmarinho/yoga,facebook/yoga,facebook/yoga,rmarinho/yoga,facebook/yoga,yihuang/css-layout,yihuang/css-layout,yihuang/css-layout,facebook/yoga,yihuang/css-layout,facebook/css-layout,facebook/css-layout,facebook/css-layout,facebook/yoga,yihuang/css-layout,facebook/css-layout,facebook/yoga,facebook/yoga