mfem: +sundials needs updated dependencies.

[balay]

For now using mfem~sundials as the dependencies wrt sundials > 6.7.0 are missing from mfem/package.py

ref: https://gitlab.com/xsdk-project/spack-xsdk/-/commit/feb950c647c4b82883ab5b0284dd1de3b7a34ce0

[balay]

Here is the error I get (with mfem+sundials):

balay@pj02:~/spack$ ./bin/spack spec xsdk@1.1.0%gcc@14.2.1
==> Error: failed to concretize `xsdk@1.1.0%gcc@14.2.1` for the following reasons:
     1. xsdk: 'amdgpu_target=none' conflicts with '+rocm'
     2. xsdk: '%gcc@14:' conflicts with '+cuda ^cuda@:12.5~allow-unsupported-compilers'
     3. xsdk: 'amdgpu_target=none' conflicts with '+rocm'
        required because conflict is triggered when amdgpu_target=none 
          required because xsdk@1.1.0%gcc@14.2.1 requested explicitly 
        required because conflict constraint +rocm 
          required because xsdk@1.1.0%gcc@14.2.1 requested explicitly 
     4. xsdk: '%gcc@14:' conflicts with '+cuda ^cuda@:12.5~allow-unsupported-compilers'
        required because conflict is triggered when %gcc@14: 
          required because xsdk@1.1.0%gcc@14.2.1 requested explicitly 
        required because conflict constraint +cuda ^cuda@:12.5~allow-unsupported-compilers 
          required because xsdk@1.1.0%gcc@14.2.1 requested explicitly 
balay@pj02:~/spack$ ./bin/spack spec xsdk@1.1.0%gcc@14.2.1~cuda~rocm
==> Error: failed to concretize `xsdk@1.1.0%gcc@14.2.1~cuda~rocm` for the following reasons:
     1. Cannot select a single "version" for package "sundials"
     2. Cannot satisfy 'sundials@:6.7.0'
     3. Cannot satisfy 'sundials@7.2.0'
     4. Cannot satisfy 'sundials@6.2.0:6.7.0'
     5. Cannot satisfy 'sundials@5:6.7'
     6. Cannot satisfy 'sundials@5.0.0:6.7.0'
     7. Cannot satisfy 'sundials@7.2.0'
        required because xsdk depends on sundials@7.2.0+hypre~int64+petsc~rocm+superlu-dist when @1.1.0~rocm 
          required because xsdk@1.1.0%gcc@14.2.1~cuda~rocm requested explicitly 
<snip>
    22. Cannot satisfy 'sundials@2.7.0:' and 'sundials@7.2.0
<snip>

[v-dobrev]

SUNDIALS 7+ is not supported in MFEM as of 09/05/2024. I've been planning to work on this for some time now, however I haven't found time to do it yet.