perl: also mark git-contacts executable

perl: also mark git-contacts executable

When installing git-contacts with Meson via -Dcontrib=contacts, the default
Perl generation fails to mark it executable. As a result, "git contacts"
reports "'contacts' is not a git command."

Unlike generate-script.sh, we aren't testing the basename here; so, glob
the script name in the case arm to match wherever the input comes from.

Signed-off-by: D. Ben Knoble <redacted>
Signed-off-by: Junio C Hamano <redacted>