Makefile.proof: Allow to override $(jobs) for `proof-allconfigs`

Change-Id: I13397d67d5f5f0860c693948b3008e9d64fc0a8e
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/libhwbase/+/474
Tested-by: Ada SPARK <gnatbot@sourcearcade.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>
1 file changed