Detect 'tv_nsec' field in 'struct stat' and set Makefile variable
NO_NSEC appropriately.
A side-effect of the above detection is that we also determine
whether 'stat.st_mtimespec' is available, so, as a bonus, set the
Makefile variable USE_ST_TIMESPEC, as well.
Signed-off-by: Reuben Hawkins <reubenhwk@gmail.com> Helped-by: Eric Sunshine <sunshine@sunshineco.com> Reviewed-by: Eric Sunshine <sunshine@sunshineco.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>