Add WCOSS2 if-block to build_tropcy_NEMS.sh for SIGIO

- the production library installation on WCOSS2 is hpc-stack and
includes updates to some library variable names
- added an if-block to build_tropcy_NEMS.sh when on WCOSS2 to set the
SIGIO variables to the new hpc-stack versions
- SIGIO_LIB4 in hpc-stack is now just SIGIO_LIB
- SIGIO_INC4 in hpc-stack is now just SIGIO_INC
- need if-block to retain support for pre-hpc-stack in operations branch
on other platforms

Refs: NOAA-EMC#399

sorc/build_tropcy_NEMS.sh

@@ -29,6 +29,11 @@ else
 fi
 
 source ../modulefiles/modulefile.storm_reloc_v6.0.0.$target
+if [ $target = "wcoss2" ]; then
+  SIGIO_LIB4=$SIGIO_LIB
+  SIGIO_INC4=$SIGIO_INC
+fi
+
 export FC=mpiifort
 export JASPER_LIB=${JASPER_LIB:-$JASPER_LIBRARY_DIRS/libjasper.a}