m4: fix gettext detection on OSX (close #5816) (cherry picked from commit d879f020aee800abaafae2e333be6da6604a3577)
m4: fix gettext detection on OSX (close #5816)
(cherry picked from commit d879f020aee800abaafae2e333be6da6604a3577)

Signed-off-by: David Fuhrmann <1118fa3e4e403c0aeed361cc3f3eb9aca4cc425c@googlemail.com>

vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1