supernova: dsp threads - avoid busy-wait in nrt synthesis

if we are in non-rt synthesis, it is friendlier to release threads than to
perform busy-waiting. if we want to optimize this further, we could wait
for a semaphore, during nrt synthesis.

Signed-off-by: Tim Blechmann <tim@klingt.org>
supernova: dsp threads - relax lockup detection

if we are using yield() as backoff strategy for nrt, we should disable
lockup detection as it is not necessary and detects some false positives

Signed-off-by: Tim Blechmann <tim@klingt.org>
sclang: library config - correcty handle library config command line argument

fixes #713

Signed-off-by: Tim Blechmann <tim@klingt.org>