add pm-gpu MOAB root

tested on perlmutter
compiled with "gnugpu" compiler environment

Author: iulian787

cime_config/machines/config_machines.xml

@@ -441,6 +441,9 @@
     <environment_variables compiler="nvidiagpu">
       <env name="MPICH_GPU_SUPPORT_ENABLED">1</env>
     </environment_variables>
+    <environment_variables compiler="gnugpu">
+      <env name="MOAB_ROOT">$SHELL{if [ -z "$MOAB_ROOT" ]; then echo /global/cfs/cdirs/e3sm/software/moab/gnugpu ; else echo "$MOAB_ROOT"; fi}</env>
+    </environment_variables>
     <environment_variables compiler="gnu.*" mpilib="mpich">
       <env name="ADIOS2_ROOT">$SHELL{if [ -z "$ADIOS2_ROOT" ]; then echo /global/cfs/cdirs/e3sm/3rdparty/adios2/2.9.1/cray-mpich-8.1.25/gcc-11.2.0; else echo "$ADIOS2_ROOT"; fi}</env>
     </environment_variables>