Add support for IFX compiler

[BenjaminTJohnson]

Description:
CRTMv3 currently supports ifort and gfortran as Fortran compilers. This issue tracks the work needed to ensure that CRTMv3 can be compiled and run correctly using the Intel IFX compiler (part of the Intel oneAPI toolchain).

Tasks:

• Identify and document any syntax or module usage in the CRTM source code that causes compilation errors with ifx
• Update CMakeLists.txt and/or compiler detection logic to support ifx
• Add ifx-specific flags to src/CMakeLists.txt, apps/CMakeLists.txt, and tests/CMakeLists.txt if needed
• Test compilation and execution of CRTM core library, test suite, and example applications with ifx
• Confirm that results are consistent with ifort and gfortran runs
• Update documentation and README.md to include ifx as a supported compiler
• (Optional) Set up CI testing with ifx if an appropriate runner is available

Notes:

The ifx compiler is more standards-compliant than ifort, which may expose latent issues or non-standard Fortran usage

Some ifort flags are deprecated or changed under ifx (e.g., OpenMP or module search paths)

Priority: Low/Medium – desirable for compatibility with modern Intel toolchains and HPC environments

[BenjaminTJohnson]

@ADCollard Jim Jung mentioned that IFX compiler support may be necessary, let us know what your thoughts are in this issue comments, thanks.

[BenjaminTJohnson]

-- The Fortran compiler identification is IntelLLVM 2023.2.0

compilation completes in RELEASE mode, just with this warning only:

[ 98%] Linking Fortran executable ../bin/test_k_matrix_test_ClearSky
ifx: command line warning #10148: option '-ip' not supported
ifx: command line warning #10148: option '-ip' not supported
[ 99%] Linking Fortran executable ../bin/test_TL_convergence_active_sensor

However, most ctests fail with segmentation faults.

[BenjaminTJohnson]

In DEBUG mode:

[ 78%] Linking Fortran executable ../bin/MWwater_IO
ld: attempted static link of dynamic object `ld/data/prod/jedi/spack-stack/spack-stack-1.8.0/envs/ue-intel-2021.10.0/install/intel/2021.10.0/netcdf-c-4.9.2-7mo7wd2/lib/libnetcdf.so: attempted static link of dynamic object `'
/data/prod/jedi/spack-stack/spack-stack-1.8.0/envs/ue-intel-2021.10.0/install/intel/2021.10.0/netcdf-c-4.9.2-7mo7wd2/lib/libnetcdf.so'
ld: cannot find -lm
ld: attempted static link of dynamic object `/data/prod/jedi/spack-stack/spack-stack-1.8.0/envs/ue-intel-2021.10.0/install/intel/2021.10.0/netcdf-c-4.9.2-7mo7wd2/lib/libnetcdf.so'
make[2]: *** [test/CMakeFiles/SpcCoeff_Inspect.dir/build.make:105: bin/SpcCoeff_Inspect] Error 1
make[1]: *** [CMakeFiles/Makefile2:1248: test/CMakeFiles/SpcCoeff_Inspect.dir/all] Error 2
make[1]: *** Waiting for unfinished jobs....

I think it's just a matter of telling FindNetCDF to use the static library instead of the dynamic one, but I can't seem to get it to do this yet.

[BenjaminTJohnson]

with openMP completely disabled (disabled openMP in CMakeLists.txt and removed calls to OMP libraries), ifx appears to work reasonably well -- suggests a serious problem with the openMP implementation in ifx, could be a library conflict of sorts, because I believe it might still be using the older ifort libomp.

All ctests except test_MWSurfEM work with RELWITHDEBINFO.
ifx version:
ifx (IFX) 2024.2.1 20240711