Flutter build script for libpng

Change-Id: Ieba221ae882d16e2e31f27ba5ca9c24adad01b5a
Reviewed-on: https://flutter-review.googlesource.com/c/third_party/libpng/+/10760
Reviewed-by: Chinmay Garde <chinmaygarde@google.com>
Commit-Queue: Jason Simmons <jsimmons@google.com>
3 files changed