The assignment and test
NRPROC='`egrep -c "^cpu[0-9]+" /proc/stat || ;`
[ "$NRPROC" = "0" ] && NRPROC = 1
returns an empty result if /proc is not mounted. As a result
runs with an unlimited number of jobs which is not very nice when you
do this on a desktop ;) .
An extra test for $NRPROC = "" should fix this.
This is fixed (using a different method) in rawhide.