Extend framework to enable modules to ship RPATH wrappers

[stderr-enst]

In the EESSI hackathon we started to work on an issue when building Software with RPATH-enabled compiler modules.
As a user, I don't really want to untangle the RPATHs for the modules library, when I am building my own code. So we thought the already existing RPATH wrappers could be automatically loaded when loading an RPATH enabled compiler module. (configurable as an easyconfig-option!)

In this issue I want to track a couple of changes that are required on the framework side, to allow modules to ship RPATH wrapper scripts when they are loaded.

There are a couple of open points to address:

1. modify module_generator.py (@boegel):
   • Add conditional statement for environment variables. Then we can ignore rpath wrappers while loading a module if something like DISABLE_RPATH_WRAPPERS is set
   • Ensure that wrappers are not put into $PATH if module is used within EasyBuild
2. modify prepare_rpath_wrappers() in toolchain.py (@stderr-enst):
   • Add function parameter to prepare_rpath_wrappers to install wrappers in a caller-given directory
   • Return directory path where wrappers were installed
   • Add option to put all wrapper scripts in a single directory (with no subdirs like gcc_wrapper/gcc)
   • Don't write rpath_wrapper_log to tempfile.gettempdir() if debug is set. This location does not necessarily exist if a module is loaded with the wrapper scripts in place
3. modify rpath_wrapper_template.sh.in:
   • Add option to read env variables RPATH_INCLUDE_DIRS and RPATH_FILTER_DIRS variables, to include/exclude directories in wrapper script (as comma-separated list) at runtime
   • Figure out a useful way to treat logging in rpath_wrapper_template.sh.in. Otherwise this will try to log to possibly non-existing /tmp/-dirs or similar
4. Add create_rpath_wrappers(), probably in toolchain.py(?):
   • Refactor create_rpath_wrappers from easybuild-easyblocks/pull/2638 into a more generic location within framework. This is probably used for other compilers in the future as well

Related PRs:

• easybuild-easyblocks/pull/2638
• easybuild-framework/pull/4003

[ocaisa]

Need to ensure that the CUDA stubs directory is excluded from the included rpaths

[stderr-enst]

Need to ensure that the CUDA stubs directory is excluded from the included rpaths

This should already happen in prepare_rpath_wrappers(): https://github.com/easybuilders/easybuild-framework/blob/develop/easybuild/tools/toolchain/toolchain.py#L964
If the rpath wrapper script also listens to environmental variables like RPATH_FILTER_DIRS, you could also exclude them even if the module is already build and loaded.