nixpkgs creates a hierarchy of 3 folders share/runtime/<PKG_NAME> for no reason ?
makes debugging harder as well as paths longer when patching so this
removes this nested folders.
`vimPackage` may not have a version attribute if it was specified using
a full name instead, such as with a `buildEnv` call. This can happen
right now on Darwin when `vimPackage` is `macvim.configure {…}`.