feat: Keep eln-cache out of my config directory.

For early-init reasons, we had to split part of syd-prelude.el out into a new
file, syd-constants.el.

users/crumb/programs/emacs/early-init.el

@@ -1,5 +1,8 @@
 ;;; early-init.el -*- lexical-binding: t; -*-
 
+(add-to-list 'load-path (file-name-concat user-emacs-directory "lib"))
+(require 'syd-constants)
+
 ;; Disable package.el; we use Straight.
 (setq package-enable-at-startup nil)
 
@@ -9,3 +12,7 @@
 (setq gc-cons-threshold
       ;; (4 gibibytes)
       (* 4 (expt 1024 3)))
+
+;; By default, Emacs will cache compilation artifacts in my personal config
+;; directory — I'm not keen on that!  Redirect it to a dedicated cache directory.
+(startup-redirect-eln-cache (file-name-concat syd-cache-dir "eln-cache"))