When nixpkgs tries to convert absolute symlinks to relative ones this currently fails with the deletion of the symlink. Tested on current master with https://patch-diff.githubusercontent.com/raw/uutils/coreutils/pull/2330.diff applied.

$ touch ed
$ result/bin/uutils-ln -s ed red
$ result/bin/uutils-ln -snrf ed red
ln: No such file or directory (os error 2)
$ lsd -lah red
lsd: red: No such file or directory (os error 2).

After the error the original symlink is deleted.