GNU sort(1) on SUSE defaults sort to one thread instead of
multithreaded sort. This is a work-around for hard to reproduce multithreaded
sort issues that have been reported in the past.

Up to now, users on SUSE had to use the command line option --parallel to get
multi-threaded sort. The environment variable OMP_NUM_THREADS was wrongly
ignored by sort(1) on SUSE.

This fix now re-enables OMP_NUM_THREADS. For OMP_NUM_THREADS=n, sort(1) will
now use n threads, as described in the info manual. If OMP_NUM_THREADS is
unset (the default), sort(1) on SUSE continues to be single-threaded.