Fix minor syntax error in link script

The last merge from develop introduced a minor syntax error in the
link script due to a bad conflict resolution. The issue is now
corrected.

Refs: NOAA-EMC#966

sorc/link_workflow.sh

@@ -194,7 +194,7 @@ fi
 if [ -d "${script_dir}/gsi_monitor.fd" ]; then
 
   cd "${top_dir}/fix" || exit 1
-    [[ ! -d gdas ]] && mkdir -p gdas || exit 1
+    [[ ! -d gdas ]] && ( mkdir -p gdas || exit 1 )
     cd gdas || exit 1
     ${LINK} "${script_dir}/gsi_monitor.fd/src/Minimization_Monitor/nwprod/gdas/fix/gdas_minmon_cost.txt"                   .
     ${LINK} "${script_dir}/gsi_monitor.fd/src/Minimization_Monitor/nwprod/gdas/fix/gdas_minmon_gnorm.txt  "                .