Unload cce prior to loading PrgEnv-gnu (chapel-lang#25934)

The cce module appears to cause a problem when used with the
PrgEnv-gnu and libfabric modules loaded, as the `hwloc`
configuration fails because -lfabric is not found. Unload the cce
module prior to loading the PrgEnv-gnu module and let it reload cce
should it want to, but this way cce isn't loaded if PrgEnv-gnu
doesn't need it.

util/build_configs/cray-internal/setenv-hpe-cray-ex-x86_64.bash

@@ -319,6 +319,9 @@ else
         local target_compiler="gcc"
         #local target_version=$gen_version_gcc
 
+        # unload cce, let the PrgEnv module load it if necessary
+        unload_module_re cce
+
         # unload any existing PrgEnv
         unload_module_re PrgEnv-