Makefile: do not set setgid bit on directories on GNU/kFreeBSD

The g+s bit on directories to make group ownership inherited is a SysVism --- BSD and most of its descendants do not need it since they do the sane thing by default without g+s. In fact, on some filesystems (but not all --- tmpfs works this way but UFS does not), the kernel of FreeBSD does not even allow non-root users to set setgid bit on directories and produces errors when one tries: $ git init --shared dir fatal: Could not make /tmp/dir/.git/refs writable by group Since the setgid bit would only mean "do what you were going to do already", it's better to avoid setting it. Accordingly, ever since v1.5.5-rc0~59^2 (Do not use GUID on dir in git init --share=all on FreeBSD, 2008-03-05), git on true FreeBSD has done exactly that. Set DIR_HAS_BSD_GROUP_SEMANTICS in the makefile for GNU/kFreeBSD, too, so machines that use glibc with the kernel of FreeBSD get the same fix. This fixes t0001-init.sh and t1301-shared-repo.sh on GNU/kFreeBSD when running tests with --root pointing to a directory that uses tmpfs. Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>