Merge pull request #16568 from gbtitus/update-tcl-modulefile-again
Don’t try to default-load the PrgEnv-gnu module on EX systems.
(Reviewed by @ronawho.)
The PrgEnv meta-modules do not exist on EX v1.3 and later. So instead
of default-loading PrgEnv-gnu on EX, simply insist that the user have
some cpe module loaded. (The cpe modules are what set PE_ENV in that
environment.) It’s not practical to load one ourselves because the cpe
modules are not meta-modules like the PrgEnv ones, and we’d have to load
all the individual things that go with it.