libv4l: v4l2-compliance needs fork

Since bump to 1.16.2, v4l2-compliance uses fork, see:
https://git.linuxtv.org/v4l-utils.git/commit/utils/v4l2-compliance/?id=79d98edd1a27233667a6bc38d3d7f8958c2ec02c

So add a patch to disable v4l2-compliance if fork is unavailable

Fixes:
 - http://autobuild.buildroot.org/results/447d792ce21c0e33a36ca9384fee46e099435ed8



Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>