On certain linux, macOS environment, there is already a system
getopt. This often creates conflict when compiling filament.
Here we alias utils::getopt to either the system getopt (if
present) or third_party/getopt.
Fixes#7551
This tool uses existing libraries: image, imageio, imageio-lite,
imagediff to perform difference comparison for on-disk images.
We refactor renderdiff to use this tool instead of using
python dependencies.
Co-authored-by: Ben Doherty <bendoherty@google.com>