Adds opt-in lz4 compression of *pkg.tar files with makepkg.
This is nice to have as an option for very fast compression
and is already installed with libarchive.
Signed-off-by: Alex Butler<alexheretic@gmail.com>
Signed-off-by: Allan McRae <allan@archlinux.org>
This allows for more easily extending the list of allowed compression
methods, as it has to be modified in only one place.
Also allow the user to specify their own preferred command + options for
source packages in addition to compiled packages. Currently,
makepkg.conf(5) erroneously claims this is already possible.
