Windows: fix utime() for read-only files
Windows: fix utime() for read-only files

Starting with 5256b00 (Use git_mkstemp_mode instead of plain mkstemp to
create object files, 2010-02-22) utime() is invoked on read-only files.
This is not allowed on Windows and results in many warnings of the form

failed utime() on .git/objects/23/tmp_obj_VlgHlc: Permission denied

during a repack.  Fix it by making the file temporarily writable.

Signed-off-by: Johannes Sixt <fd432345609ae4d58c1aa629cb66ba96d1391622@kdbg.org>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git