For systems with a missing or broken perl, it is nicer to
explicitly say "we don't want perl" because:
1. The Makefile knows not to bother with Perl-ish things
2. We can print a more user-friendly error message
than "foo is not a git command" or whatever the broken
perl might barf
3. Test scripts that require perl can mark themselves and
such and be skipped
This patch implements parts (1) and (2). The perl/
subdirectory is skipped entirely, gitweb is not built, and
any git commands which rely on perl will print a
human-readable message and exit with an error code.
This patch is based on one from Robin H. Johnson.
Signed-off-by: Jeff King <email@example.com>
Signed-off-by: Junio C Hamano <firstname.lastname@example.org>