bug#75022: 31.0.50; --init-directory sets user-emacs-directory after user eln-cache is set

[Jordan Isaacs]

In startup.el, the user-emacs-directory and the user eln-cache are set up 
before processing command line args.
The user eln-cache is then gets updated after the early-init.el is loaded. This 
leaves a gap where early-init.el is
loaded without the correct eln-cache directory. This means there will always be 
a cache miss if the early-init.eln
file was in the `--init-directory`.

To fix this, either `--init-directory` needs to be read before setting up the 
user eln-cache, or a call to `startup--update-eln-cache` needs to be called 
after command line args are processed since user-emacs-directory may have 
changed (from `--init-directory`).