Project.pm: create hooks directory group writable
In
85e92c7d (hooks: make sure hooks directory exists before writing
hooks, 2014-11-17), we started making sure the hooks directory exists
before trying to install hooks by creating it if necessary.
However, we forgot to be careful and allow group write when doing
so. Normally git init will create it for us and we will make sure
it has the correct permissions, but just in case something goes
wrong there.
We need group-writable in case the hooks directory was created via
the web interface but the hooks are being updated via the install
user (i.e. $mirror_user).
Signed-off-by: Kyle J. McKay <mackyle@gmail.com>