Enable NEON support on MacOS / ARM64

Required to support building for M1 Macs.

Bug: https://github.com/flutter/flutter/issues/69221

Patch authored by Matej Knopp <matej.knopp@gmail.com>

Change-Id: I78fd38d31c7b1a2ea16af651f6b950888511bd44
Reviewed-on: https://flutter-review.googlesource.com/c/third_party/libpng/+/12660
Reviewed-by: Kaushik Iska <kaushikiska@google.com>
Commit-Queue: Chris Bracken <cbracken@google.com>
1 file changed