Verify that user-defined-trusted-dirs paths are used by the dynamic loader

[bedroge]

ld.so --help actually prints all search paths:

Shared library search path:
  (libraries located via /cvmfs/software.eessi.io/versions/2023.06/compat/linux/x86_64/etc/ld.so.cache)
  /cvmfs/software.eessi.io/versions/2023.06/compat/linux/x86_64/lib64 (system search path)
  /cvmfs/software.eessi.io/versions/2023.06/compat/linux/x86_64/usr/lib64 (system search path)
  /cvmfs/software.eessi.io/host_injections/2023.06/compat/linux/x86_64/lib (system search path)

We can use that for the ReFrame test (https://github.com/EESSI/compatibility-layer/blob/main/test/compat_layer.py#L212) and in the Ansible role (https://github.com/EESSI/compatibility-layer/blob/main/ansible/playbooks/roles/compatibility_layer/tasks/set_glibc_trusted_dirs.yml#L19) to actually verify if the right paths are being picked up by our glibc installation.