With pkgvars.py in your PATH, and a PKGBUILD in your current directory,
run bash pkgvars.sh. The output is formatted JSON.
A patch for Pacman (makepkg) and an updated Pacman PKGBUILD are included,
along with an example working split PKGBUILD
and an example PKGBUILD with a custom array,
to show how custom arrays are not handled by this script.