FST: detect detectors with no raw data also on macOS

The check for detectors that produced only empty raw files compared the
output of wc -l with "0". BSD wc, as on macOS, pads its count with
spaces, so the comparison never matched and an empty raw output went
unnoticed: the TRD raw files of a run were all empty, and the test only
failed later, when no CTF had been written. grep -c prints the bare count
on every platform.

Author: ktf

prodtests/full_system_test.sh

@@ -222,7 +222,7 @@ if [[ $BEAMTYPE == "PbPb" ]] && [ $NEvents -ge 5 ] ; then
   CHECK_DETECTORS_RAW+=" EMC PHS HMP"
 fi
 for i in $CHECK_DETECTORS_RAW; do
-  if [[ `ls -l raw/$i/*.raw | awk '{print $5}' | grep -v "^0\$" | wc -l` == "0" ]]; then
+  if [[ `ls -l raw/$i/*.raw | awk '{print $5}' | grep -c -v "^0\$"` == "0" ]]; then
     echo "ERROR: Full system test did generate no raw data for $i"
     exit 1
   fi