* Use `--init-directory` in Emacs 29+
This will allow a few advantages:
- We can load `early-init.el` file properly, fixing Flash Of Unstyled
Contents (FOUC) issues and improving the performance slightly
- Eventually we can drop `default.el` file loading in Home-Manager
module. Not done here since this would complicate the code without
necessity, however this can be done once Emacs 29+ is default
* Fix build in Emacs <29
* Add #checks.<arch>.init-example-el-emacsGit
* Add .#checks.x86_64-linux.init-example-el-emacsGit to CI
* Fix review issues
* Move config files to share/emacs.d
* Separate tests in two steps
* Add TODOS
* Simplify emacs-dir generation
I've been playing around with a custom home-manager module that extends this one that generates `init.el` programmatically. However, I can't use the `doom.d` folder it generates, because `doomPrivateDir` calls `builtins.path` which fails if given a `/nix/store` path.
This PR fixes `doomPrivateDir` to only call `builtins.path` if the given `path` is not already a `/nix/store` path.
