Rewrite xorg.lndir

[viperML]

Symlinkjoin, which wrapper-manager uses internally, uses xorg.lndir.

It has a problem: it doesn't recurse into symlinks that point to directories, but rather just symlink the symlink itself.

This is what you would expect from this tool, but for the use-case of wrapper-manager it makes it harder for patching files, as you have to "unwind" the nested symlinks to be able to have a mutable directory, instead of a symlink to a directory:

wrapper-manager/modules/base.nix

Lines 249 to 257 in f2b0bec

	# Some derivations have nested symlinks here
	if [[ -d $out/share/applications && ! -w $out/share/applications ]]; then
	echo "Detected nested symlink, fixing"
	temp=$(mktemp -d)
	cp -v $out/share/applications/* $temp
	rm -vf $out/share/applications
	mkdir -pv $out/share/applications
	cp -v $temp/* $out/share/applications
	fi

Ideally we would have a lndir clone that can unwind symlinks, maybe only for share/applications/