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

[Jordan Isaacs]

Because it is read only, there is no reason not to byte compile everything. I 
just make it part of the build step when packaging up my configuration.

The reasoning for why I byte compile though seems irrelevant, it’s a bug with a 
simple fix. The eln-cache path isn’t staying in sync with user-emacs-directory. 

    (let ((old-face-font-rescale-alist face-font-rescale-alist))
      (unwind-protect
          (command-line)
+  (when (featurep 'native-compile)
+     (startup--update-eln-cache))