Makefile: allow building without .git
Makefile: allow building without .git

Use the same strategy as podman for obtaining the commit id, so we
don't fail if this is a release without the ".git" directory.

Signed-off-by: Sergio Lopez <2a49a3230a2bdfb748295d04d38c6f188489c774@redhat.com>

nalind/buildah-1,nalind/buildah-1,TomSweeneyRedHat/buildah,TomSweeneyRedHat/buildah,nalind/buildah-1,TomSweeneyRedHat/buildah