Clear error when `install_cuda_host_injections` fails to run easybuild

[Flamefire]

The script first tries to run eb CUDA-x.y.eb and if that fails runs eb -S '^CUDA-* and if that fails it just shows a generic error.

However if the actual failure is with eb itself that message is misleading. E.g.:

# /cvmfs/software.eessi.io/versions/2023.06/scripts/gpu_support/nvidia/install_cuda_host_injections.sh --cuda-version 12.8.6 --temp-dir /tmp/ --accept-cuda-eula                                                          
Attempting to load an EasyBuild module to do actual install
ERROR: You seem to be running EasyBuild with root privileges which is not wise, so let's end this here.
ERROR: You seem to be running EasyBuild with root privileges which is not wise, so let's end this here.
ERROR: The easyconfig CUDA-12.8.6.eb was not found in EasyBuild version:
  This is EasyBuild 5.1.0 (framework: 5.1.0, easyblocks: 5.1.0) on host c144.
You either need to give a different version of CUDA to install _or_ 
use a different version of EasyBuild for the installation.

I've seen a similar failure when something else fails during initialization, e.g. pre-creating the modules/all folder.

It would be good if the script could detect such cases and report an error of the kind "EasyBuild failed to run, check the above output for reasons"