bug#42558: ‘guix pack -RR’: audit library is dynamically linked

["Ludovic Courtès" <ludovic.courtes@inria.fr>]

The audit library created by ‘guix pack -RR’, called ‘pack-audit.so’, is
dynamically-linked.  Thus, it cannot be loaded (unless there are working
libgcc.so and libc.so in the search path?), leading to failures like
this:

--8<---------------cut here---------------start------------->8---
$ GUIX_EXECUTION_ENGINE=performance ./bin/sinfo --version
ERROR: ld.so: object '/…/lcourtes/tmp/t/gnu/store/0n6nnvzgxyisg0bszb5zqxp2gzdwh7h3-pack-audit.so' cannot be loaded as audit interface: cannot open shared object file; ignored.
/…/lcourtes/tmp/t/gnu/store/3dhy2f3djmm1h5ix5aa84lrskxzrl6d0-slurm-19.05.3-2/bin//sinfo: error while loading shared libraries: libslurmfull.so: cannot open shared object file: No such file or directory
--8<---------------cut here---------------end--------------->8---

The root cause is that ‘pack-audit.so’ NEEDs libgcc_s.so, which on this
machine could not be loaded, and thus resolving the other dependencies
of the wrapped executable, like ‘libslurmfull.so’ here, fails.

Ludo’.