Enable rt.sh to run with a container w/ llvm mixed compilers

[mark-a-potts]

Commit Queue Requirements:

• Fill out all sections of this template.
• All sub component pull requests have been reviewed by their code managers.
• Run the full Intel+GNU RT suite (compared to current baselines) on either Hera/Derecho/Hercules
• Commit 'test_changes.list' from previous step

---

Description:

This PR will enable rt.sh to run using containerized spack-stack version 1.9.1 using mixed intel/llvm compilers and adds a new option to "RUN_ONLY" if the "COMPILE_ONLY" has previously been run.

Commit Message:

* UFSWM - modifies rt.sh and Intel flags used to compile. Adds the option to run tests only (no compile) 
  

Priority:

• Normal

Git Tracking

UFSWM:

• Closes #
• None

Sub component Pull Requests:

• None

UFSWM Blocking Dependencies:

• None

---

Changes

Regression Test Changes (Please commit test_changes.list):

• No Baseline Changes.

Input data Changes:

• None.

Library Changes/Upgrades:

• No Updates

---

Testing Log:

• RDHPCS
  • Hera
  • Orion
  • Hercules
  • GaeaC5
  • GaeaC6
  • Derecho
• WCOSS2
  • Dogwood/Cactus
  • Acorn
• CI
• opnReqTest (complete task if unnecessary)

[ulmononian]

this is something i have wanted to see for a long time.

is this going to enable users to run the ufs-wm 'run' step on an existing fv3.exe to just check if the run will pass (without having to wait for a re-compile)?

[mark-a-potts]

That is the idea, but it isn't working yet, unfortunately.

[gspetro-NOAA]

@mark-a-potts @ulmononian @EdwardSnyder-NOAA @jkbk2004 Is this PR still planned/desired? I know there has been talk of containerizing the RTs, but it seems like someone else would need to continue the work that Mark started. Could we close this PR an open a new one once it's ready?