OLMT-E3SM compatibility

[walkeranthonyp]

I don't think the current HEAD of master on both E3SM and OLMT repos are compatible. I just tried running:

python site_fullrun.py --site US-UMB --caseidprefix MYTEST --nyears_ad_spinup 200 --nyears_final_spinup 400 --tstep 1 --cpl_bypass --spinup_vars --sitegroup ACMEeval --machine cades

With the HEAD of OLMT and the HEADs of the E3SM branches master and dmricciuto/machinefiles/cades-slurm. I was getting pio build errors and the CMAKE error that Liz was getting (or similar). Back tracking on Liz's home space I checked out commit 80dd0a3 of OLMT and ran a successful build of the above command and the CASES were submitted and are now running.

It might be handy to add the tested branches and commits of both repos to the OLMT README.