shr_cal unit tests should have only a single ESMF_Initialize and ESMF_Finalize

[billsacks]

CTSM's unit tests needed some changes to prevent multiple calls to ESMF_Initialize and ESMF_Finalize within the same executable. (It worked to have these multiple calls when we used the ESMF WRF Time manager, but no longer works with the real ESMF library.) I think the shr_cal unit tests need similar changes (only initialize if not yet initialized; finalize in the teardown of the executable rather than the teardown of each test).

[billsacks]

I was having trouble getting the unit tests running on either my Mac or derecho. But I'm able to get further if I do this on derecho:

module load esmf
export ESMF_ROOT=/glade/u/apps/derecho/24.12/spack/opt/spack/esmf/8.8.0/cray-mpich/8.1.29/oneapi/2024.2.1/ypx5

Then run the unit tests with:

python CIME/tests/scripts_regression_tests.py CIME.tests.test_sys_unittest

(The setting of ESMF_ROOT is needed to access the FindESMF.cmake module that's bundled with ESMF.)

@jedwards4b - I was under the impression that you got the unit tests working with the ESMF library a few months ago, so I was puzzled that I couldn't get them working more out-of-the-box. Am I right in thinking that you got them working? If so, do you have a simple set of instructions for how to get them to run on derecho so that I can do this consistently to what you did? (I considered making changes similar to what I just did for CTSM's top-level CMake, but I think those changes would end up in CIME's CMakeLists.txt, and I'm not sure if it's acceptable to put ESMF dependencies there.)

[billsacks]

I'm thinking that the intent is now to run the share unit tests from the CMakeLists.txt in share rather than the one in cime. But I'm still having trouble getting these running on derecho.

This issue feels low priority: I only got into this because I noticed it when solving the similar issue in CTSM (which was higher priority, since people are more actively working with the unit tests in CTSM). I think that resolving it will be straightforward once I can get the unit tests to build somewhere, but I don't feel that I can spend the time right now trying to mess around with this unit test build, given my current funding / priorities. So where that leaves things is: @jedwards4b , if you know what I need to do to get the unit tests building on derecho or some other place where I can test this, then I can work on this; if you don't know off-hand, then I think this should be put on the back burner for now.

[billsacks]

I have gotten the unit tests working on both my Mac and derecho, so I can address this at some point... though it's low priority so I'm not going to try to tackle it right now.