Revert "Make the installation target of git-gui a little less chatty"

This reverts commit c289f6fa1f8642a5caf728ef8ff87afd5718cd99.

Junio pointed out that Alex's change breaks in some cases, like
when V=1, and is more verbose than it should be even if that worked.
I'm backing it out and redoing it.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>