According to POSIX specification uname(2) must return -1 on failure
and a non-negative value on success. Although many implementations
do return 0 on success it is valid to return any positive value for
success. In particular, Solaris returns 1.
Signed-off-by: Charles Bailey <cbailey32@bloomberg.net> Reviewed-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>