Stop making links for unbuilt components

After switching to submodules, the link script could no longer use
the existence of directories to determine which executables to link.
Now it instead looks for the existence of the build directory.

Refs NOAA-EMC#2141

sorc/link_workflow.sh

@@ -199,7 +199,7 @@ fi
 #------------------------------
 #--add GDASApp files
 #------------------------------
-if [[ -d "${HOMEgfs}/sorc/gdas.cd" ]]; then
+if [[ -d "${HOMEgfs}/sorc/gdas.cd/build" ]]; then
   cd "${HOMEgfs}/ush" || exit 1
   ${LINK_OR_COPY} "${HOMEgfs}/sorc/gdas.cd/ush/ufsda"                              .
   ${LINK_OR_COPY} "${HOMEgfs}/sorc/gdas.cd/ush/jediinc2fv3.py"                     .
@@ -261,15 +261,15 @@ for ufs_utilsexe in emcsfc_ice_blend emcsfc_snow2mdl global_cycle; do
 done
 
 # GSI
-if [[ -d "${HOMEgfs}/sorc/gsi_enkf.fd" ]]; then
+if [[ -d "${HOMEgfs}/sorc/gsi_enkf.fd/install" ]]; then
   for gsiexe in enkf.x gsi.x; do
     [[ -s "${gsiexe}" ]] && rm -f "${gsiexe}"
     ${LINK_OR_COPY} "${HOMEgfs}/sorc/gsi_enkf.fd/install/bin/${gsiexe}" .
   done
 fi
 
 # GSI Utils
-if [[ -d "${HOMEgfs}/sorc/gsi_utils.fd" ]]; then
+if [[ -d "${HOMEgfs}/sorc/gsi_utils.fd/install" ]]; then
   for exe in calc_analysis.x calc_increment_ens_ncio.x calc_increment_ens.x \
     getsfcensmeanp.x getsigensmeanp_smooth.x getsigensstatp.x \
     interp_inc.x recentersigp.x
@@ -280,7 +280,7 @@ if [[ -d "${HOMEgfs}/sorc/gsi_utils.fd" ]]; then
 fi
 
 # GSI Monitor
-if [[ -d "${HOMEgfs}/sorc/gsi_monitor.fd" ]]; then
+if [[ -d "${HOMEgfs}/sorc/gsi_monitor.fd/install" ]]; then
   for exe in oznmon_horiz.x oznmon_time.x radmon_angle.x \
     radmon_bcoef.x radmon_bcor.x radmon_time.x
   do
@@ -290,7 +290,7 @@ if [[ -d "${HOMEgfs}/sorc/gsi_monitor.fd" ]]; then
 fi
 
 # GDASApp
-if [[ -d "${HOMEgfs}/sorc/gdas.cd" ]]; then
+if [[ -d "${HOMEgfs}/sorc/gdas.cd/build" ]]; then
   declare -a JEDI_EXE=("fv3jedi_addincrement.x" \
                        "fv3jedi_diffstates.x" \
                        "fv3jedi_ensvariance.x" \