Right now the `zsh.prezto` module ignores the contents of the
`zsh.{profile,login,logout,env}Extra` options, so it means that if you
try to set, e.g., `zsh.profileExtra = "something";` this option will be
(silently) ignored.
This commit fixes another issue: since the main `zsh` module sets
`home.file."${relToDotDir".zshenv"}".text` while `zsh.prezto` set the
same file using `.source`, `zsh.prezto` would have priority so the
environment variables from Home-Manager would not be loaded in non-NixOS
systems. Now that we are using `.text` for both, the issue is fixed.
5f36563a5c