Update NDK version to 12
Update NDK version to 12

Summary: This diff updates the NDK version from 10 to 12

Reviewed By: emilsjolander

Differential Revision: D4634938

fbshipit-source-id: 6a9cbc48dbcbda4674d6460120c7a0d8abd626ab

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