Add --quiet option to lwptool

Add --quiet option to lwptool

Add an option to lwptool, called --quiet, to suppress printing the
literal commands run. On error, we still print the exact failed
command to stderr.

For "pretty" V=0 builds, use this new option, to make our
lwptool-using compile rules look more like our other compile rules.

Change-Id: I3fed6db3205f8de5e275e9b70aba9e1995afd02f
Reviewed-on: https://gerrit.openafs.org/13594
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>