[Bandwidth tests] Use LBN_BUILD_JOBS to properly set n_threads on Moore in BW test

FYI @clemenci

The Moore bandwidth tests were recently moved over to a new 64-core machine, but they should only be using 16 threads for the Moore event loop. They're currently using everything through nproc - this changes it to use the LBN_BUILD_JOBS environment variable, defaulting to single-thread if this variable not set (e.g. when running locally).

scripts/benchmark-scripts/Moore_bandwidth_test.sh

@@ -119,7 +119,7 @@ case $PROCESS in
     ;;
     hlt2)
     N_EVTS=1e5
-    MOORE_THREADS=$(nproc)
+    MOORE_THREADS=${LBN_BUILD_JOBS:-1} # Default to single-threaded
     TEST_PATH_PREFIX='$HLT2CONFROOT/tests/options/bandwidth/'
     EVENT_SIZE_UPPER_LIMIT=200
     GAUDIRUN_INPUT_PROCESS="Hlt2"
@@ -141,7 +141,7 @@ case $PROCESS in
     ;;
     spruce)
     N_EVTS=1e5
-    MOORE_THREADS=$(nproc)
+    MOORE_THREADS=${LBN_BUILD_JOBS:-1} # Default to single-threaded
     TEST_PATH_PREFIX='$HLT2CONFROOT/tests/options/bandwidth/'
     EVENT_SIZE_UPPER_LIMIT=300
     GAUDIRUN_INPUT_PROCESS="Spruce"