wscript: fix installing pre-commit with 'git worktree'

wscript: fix installing pre-commit with 'git worktree'

.git is not always a directory, with 'git worktree' it's a file.

'git rev-parse --git-path hooks' is the generic way to find the
patch for the githooks.

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andreas Schneider <asn@samba.org>
Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Thu Aug 12 08:56:13 UTC 2021 on sn-devel-184

(cherry picked from commit 8858cf72af1cc15784749e58f184559a839dd4ef)

Autobuild-User(v4-14-test): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(v4-14-test): Thu Aug 12 11:49:18 UTC 2021 on sn-devel-184