Fix validateOptions to match kpod
Fix validateOptions to match kpod

This patch will allow for the possibility of a valid "-"
option value.  This is often used for taking from STDIN,
and should future proof us from this breaking if ever added.

Signed-off-by: Daniel J Walsh <7800de746fd39599bc46177380ea6aede7e31e16@redhat.com>

projectatomic/buildah,ipbabble/buildah,nalind/buildah,rhatdan/buildah,ipbabble/buildah,nalind/buildah-1,rhatdan/buildah,nalind/buildah-1,nalind/buildah-1,TomSweeneyRedHat/buildah,rhatdan/buildah,projectatomic/buildah,TomSweeneyRedHat/buildah,TomSweeneyRedHat/buildah,nalind/buildah,projectatomic/buildah