refactor(native-comp): improve native-comp env setup patch

Instead of patching emacs sources before building Emacs, we can use
site-start.el instead for a much cleaner way of setting LIBRARY_PATH
before the user config is loaded.

patches/native-comp-env-setup.diff.erb

@@ -1,57 +0,0 @@
-diff --git a/lisp/emacs-lisp/comp.el b/lisp/emacs-lisp/comp.el
-index 638d4b274c..2599211936 100644
---- a/lisp/emacs-lisp/comp.el
-+++ b/lisp/emacs-lisp/comp.el
-@@ -4224,6 +4224,52 @@ native-compile-async
-   (let ((load (not (not load))))
-     (native--compile-async files recursively load selector)))
- 
-+;;;###autoload
-+(defun native-compile-setup-environment-variables (&rest _args)
-+  "Ensure LIBRARY_PATH is set correctly when libgccjit is bundled."
-+  (when (and (eq system-type 'darwin)
-+             (string-match-p "\.app\/Contents\/MacOS\/?$"
-+                             invocation-directory))
-+    (let* ((library-path-env (getenv "LIBRARY_PATH"))
-+           (devtools-dir
-+            "/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/lib")
-+           (gcc-dir (expand-file-name
-+                     "<%= app_bundle_relative_lib_dir %>"
-+                     invocation-directory))
-+           (darwin-dir (expand-file-name
-+                        "<%= app_bundle_relative_darwin_lib_dir %>"
-+                        invocation-directory))
-+           (lib-paths (list)))
-+
-+      (if library-path-env
-+          (push library-path-env lib-paths))
-+      (if (file-directory-p devtools-dir)
-+          (push devtools-dir lib-paths))
-+      (push darwin-dir lib-paths)
-+      (push gcc-dir lib-paths)
-+
-+      (setenv "LIBRARY_PATH" (mapconcat 'identity lib-paths ":"))))
-+
-+  ;; Remove advice, as it only needs to run once.
-+  (advice-remove 'native-compile
-+                 'native-compile-setup-environment-variables)
-+  (advice-remove 'comp--native-compile
-+                 'native-compile-setup-environment-variables)
-+  (advice-remove 'native-compile-async
-+                 'native-compile-setup-environment-variables)
-+  (advice-remove 'native--compile-async
-+                 'native-compile-setup-environment-variables))
-+
-+;; Ensure environment setup runs before any native compilation.
-+(advice-add 'native-compile :before
-+            'native-compile-setup-environment-variables)
-+(advice-add 'comp--native-compile :before
-+            'native-compile-setup-environment-variables)
-+(advice-add 'native-compile-async :before
-+            'native-compile-setup-environment-variables)
-+(advice-add 'native--compile-async :before
-+            'native-compile-setup-environment-variables)
-+
- (provide 'comp)
- 
- ;; LocalWords: limplified limplified limplification limplify Limple LIMPLE libgccjit elc eln