bcachefs-tools: Prettify make output

bcachefs-tools: Prettify make output

Make the default "make" output look more like kbuild; this makes
errors and warnings much easier to spot. "Make V=1" will revert to
showing the full command lines.

This is done by redefining some implicit rules to add the echo and
the quiet variable.  These changes are similar to those in xfsprogs.
and btrfs-progs

This patch also silences things if pytest-3 is not found.

Signed-off-by: Eric Sandeen <sandeen@sandeen.net>