bug#43984: `--with-graft=...` doesn't work with packages of different length name/version

[pkill9]

As expected, if you attempt to graft a package's dependency, and it's
name + version is different length to the original dependency, then it
will fail to graft.

Maybe if the length/version is different, then a symlink could be
created in the store pointing to the new dependency, with a
name/version that matches the length of the original dependency's store
name? Perhaps this new name/version could be something like
/gnu/store/...-original-dependency-name-gggggg, where 'g..' matches the
length of the version of the original dependency. The many 'g's would
make it clear that it is a graft. Then if someone looks in the store,
they would see it's a symlink too.