ignore some tar warnings to prevent log noise

[rspier]

mldistwatch spewed a bunch of these to the logs

/usr/bin/tar: Ignoring unknown extended header keyword 'LIBARCHIVE.xattr.com.apple.provenance'

Looks like we can quiet them with: --warning=no-unknown-keyword

[akarelas]

I keep getting these warnings with Carton when installing Mojolicious and several other CPAN modules.

[andk]

Thanks, everybody, #558 was just merged and deployed