systemd: remove references to $out/lib/systemd/catalog

On aarch64 we "leak" a reference to $out/lib/systemd/catalog in the lib
output. The result of that is a dependency cycle between $out and $lib.
Thus nix (rightfully) marks the build as failed. That reference
originates from an array of strings (catalog_file_dirs) in systemd
(src/src/journal/catalog.{c,h}).  The only consumer (as of v242) of the
symbol is the main function of journalctl.  Still libsystemd.so contains
the VALUE but not the symbol.  Systemd seems to be properly using
function & data sections together with the linker flags to garbage
collect unused sections (-Wl,--gc-sections).  For unknown reasons those
flags do not eliminate the unused string constants, in this case on
aarch64-linux. The hacky way is to just remove the reference after we
finished compiling.  Since it can not be used (there is no symbol to
actually refer to it) there should not be any harm.  It is a bit odd and
I really do not like starting these kind of hacks but there doesn't seem
to be a straight forward way at this point in time.

The reference will be replaced by the same reference the usual nukeRefs
tooling uses.  The standard tooling can not / should not be uesd since
it is a bit too excessive and could potentially do us some (more) harm.