base-filesystem: do not attempt to create a /lib64 -> /usr/lib/<tuple> symlink

base-filesystem: do not attempt to create a /lib64 -> /usr/lib/<tuple> symlink

In multi-arch distributions (debian and derivatives) multiarch tuples under
/usr/lib are used, such as /usr/lib/x86_64-linux-gnu/ but the /lib64 symlink
should never point there, it should always point to /usr/lib64, as that's
how they are set up by distribution-specific tools.

https://packages.debian.org/bookworm/amd64/libc6-i386/filelist
https://packages.debian.org/bookworm/mipsel/libc6-mips64/filelist
https://salsa.debian.org/md/usrmerge/-/blob/master/convert-usrmerge?ref_type=heads#L295
https://salsa.debian.org/md/usrmerge/-/blob/master/convert-usrmerge?ref_type=heads#L517
http://bugs.debian.org/1076491

Fixes https://github.com/systemd/systemd/issues/33919