Android NDK r21c (build 6472646)
Merge cherrypicks of [1275206, 1275207, 1275375, 1275579, 1275580, 1275581, 1275582, 1275583, 1275584, 1275585, 1275586, 1275587, 1275588, 1275589, 1275398, 1275399, 1275223, 1275540, 1275541, 1275542, 1275435] into ndk-release-r21

Change-Id: I193e3ed92c74a3a730b44490b43a583ff93dc5d3