Allow for compiler+accelerator specific MPI overrides

[ocaisa]

Alternative to #230 where we focus only on the potential need for CUDA/ROCm variants.

This also opens the door to other types of variants (but the options here would be multiplicative so I haven't included that until we hit a need for it).

[ocaisa]

Example of the output

# Set things up
ocaisa@~/EESSI/software-layer-scripts(additional_rpath_fallbacks)$ export EESSI_ACCELERATOR_TARGET_OVERRIDE=accel/nvidia/cc86
ocaisa@~/EESSI/software-layer-scripts(additional_rpath_fallbacks)$ module load EESSI/2025.06
Module for EESSI/2025.06 loaded successfully
{EESSI/2025.06} ocaisa@~/EESSI/software-layer-scripts(additional_rpath_fallbacks)$ echo $MODULEPATH
/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neoverse_n1/accel/nvidia/cc80/modules/all:/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neoverse_n1/modules/all:/cvmfs/software.eessi.io/versions/2025.06/software/linux/aarch64/neoverse_n1/accel/nvidia/cc80/modules/all:/cvmfs/software.eessi.io/versions/2025.06/software/linux/aarch64/neoverse_n1/modules/all:/cvmfs/software.eessi.io/init/modules
{EESSI/2025.06} ocaisa@~/EESSI/software-layer-scripts(additional_rpath_fallbacks)$ module load EESSI-extend
-- Using /tmp/$USER as a temporary working directory for installations, you can override this by setting the environment variable WORKING_DIR and reloading the module (e.g., /dev/shm is a common option)
Configuring for use of EESSI_USER_INSTALL under /home/ocaisa/eessi
-- To create installations for EESSI, you _must_ have write permissions to /home/ocaisa/eessi/versions/2025.06/software/linux/aarch64/neoverse_n1
-- You may wish to configure a sources directory for EasyBuild (for example, via setting the environment variable EASYBUILD_SOURCEPATH) to allow you to reuse existing sources for packages.

# Pretend to want  to do a build
{EESSI/2025.06} ocaisa@~/EESSI/software-layer-scripts(additional_rpath_fallbacks)$ eb OSU-Micro-Benchmarks-7.5.1-gompi-2025b-CUDA-12.9.1.eb --stop prepare --rebuild --hooks=./eb_hooks.py
== Temporary log file in case of crash /tmp/eb-uflhewm6/easybuild-0ha7tv9j.log
== found valid index for /cvmfs/software.eessi.io/versions/2025.06/software/linux/aarch64/neoverse_n1/software/EasyBuild/5.3.0/easybuild/easyconfigs, so using it...
== Running parse hook for OSU-Micro-Benchmarks-7.5.1-gompi-2025b-CUDA-12.9.1.eb...
== found valid index for /cvmfs/software.eessi.io/versions/2025.06/software/linux/aarch64/neoverse_n1/software/EasyBuild/5.3.0/easybuild/easyconfigs, so using it...
== Running parse hook for gompi-2025b.eb...
...
== Running parse hook for lfbf-2025b.eb...
== processing EasyBuild easyconfig
/cvmfs/software.eessi.io/versions/2025.06/software/linux/aarch64/neoverse_n1/software/EasyBuild/5.3.0/easybuild/easyconfigs/o/OSU-Micro-Benchmarks/OSU-Micro-Benchmarks-7.5.1-gompi-2025b-CUDA-12.9.1.eb
== building and installing OSU-Micro-Benchmarks/7.5.1-gompi-2025b-CUDA-12.9.1...
  >> installation prefix: /home/ocaisa/eessi/versions/2025.06/software/linux/aarch64/neoverse_n1/software/OSU-Micro-Benchmarks/7.5.1-gompi-2025b-CUDA-12.9.1
== fetching files and verifying checksums...
== Running pre-fetch hook...
  >> sources:
  >> /tmp/ocaisa/easybuild/sources/o/OSU-Micro-Benchmarks/osu-micro-benchmarks-7.5.1.tar.gz [SHA256: 160d0d5e3c3cb022520ecb247e9875bb0973b1d3cadccd6c17624f8407c52e22]
== ... (took < 1 sec)
== creating build dir, resetting environment...
  >> build dir: /tmp/ocaisa/easybuild/build/OSUMicroBenchmarks/7.5.1/gompi-2025b-CUDA-12.9.1
== Running post-ready hook...

WARNING: Deprecated functionality, will no longer work in EasyBuild v6.0: Easyconfig parameter 'parallel' is deprecated, use 'max_parallel' or the parallel property instead.; see
https://docs.easybuild.io/deprecated-functionality/ for more information

== ... (took < 1 sec)
== unpacking...
  >> running shell command:
        tar xzf /tmp/ocaisa/easybuild/sources/o/OSU-Micro-Benchmarks/osu-micro-benchmarks-7.5.1.tar.gz
        [started at: 2026-05-14 16:03:37]
        [working dir: /tmp/ocaisa/easybuild/build/OSUMicroBenchmarks/7.5.1/gompi-2025b-CUDA-12.9.1]
        [output and state saved to /tmp/eb-uflhewm6/run-shell-cmd-output/tar-gfx7xw93]
  >> command completed: exit 0, ran in < 1s
== ... (took < 1 sec)
== patching...
== ... (took < 1 sec)
== preparing...
== Running pre-prepare hook...
== Updated rpath_override_dirs (to allow overriding MPI family OpenMPI):
/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neoverse_n1/rpath_overrides/OpenMPI/system-CUDA-12.9.1/lib:/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neover
se_n1/rpath_overrides/OpenMPI/system-CUDA-12.9.1/lib64:/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neoverse_n1/rpath_overrides/OpenMPI/system/lib:/cvmfs/software.eessi.io/host_injec
tions/2025.06/software/linux/aarch64/neoverse_n1/rpath_overrides/OpenMPI/system/lib64
  >> loading toolchain module: gompi/2025b
== ... (took < 1 sec)
...

[ocaisa]

Increased the complexity a bit but it might be necessary:

== Updated rpath_override_dirs (to allow overriding MPI family OpenMPI):
/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neoverse_n1/rpath_overrides/OpenMPI/system-GCC-CUDA-12.9.1/lib:/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/ne
overse_n1/rpath_overrides/OpenMPI/system-GCC-CUDA-12.9.1/lib64:/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neoverse_n1/rpath_overrides/OpenMPI/system-GCC/lib:/cvmfs/software.eessi.i
o/host_injections/2025.06/software/linux/aarch64/neoverse_n1/rpath_overrides/OpenMPI/system-GCC/lib64:/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neoverse_n1/rpath_overrides/OpenMPI
/system/lib:/cvmfs/software.eessi.io/host_injections/2025.06/software/linux/aarch64/neoverse_n1/rpath_overrides/OpenMPI/system/lib64
  >> loading toolchain module: gompi/2025b