feat: support for MPS garbage collector (igc)

And remove/disable gcmh if running the IGC build.

lisp/doom-start.el

@@ -84,10 +84,11 @@
 ;; when it's idle. However, if the idle delay is too long, we run the risk of
 ;; runaway memory usage in busy sessions. And if it's too low, then we may as
 ;; well not be using gcmh at all.
-(setq gcmh-idle-delay 'auto  ; default is 15s
-      gcmh-auto-idle-delay-factor 10
-      gcmh-high-cons-threshold (* 64 1024 1024))  ; 64mb
-(add-hook 'doom-first-buffer-hook #'gcmh-mode)
+(unless (featurep 'igc)
+  (setq gcmh-idle-delay 'auto  ; default is 15s
+        gcmh-auto-idle-delay-factor 10
+        gcmh-high-cons-threshold (* 64 1024 1024))  ; 64mb
+  (add-hook 'doom-first-buffer-hook #'gcmh-mode))
 
 
 ;;; Disable UI elements early

lisp/doom.el

@@ -155,6 +155,8 @@
     (push 'jansson features))
 (if (string-match-p "HARFBUZZ" system-configuration-features) ; no alternative
     (push 'harfbuzz features))
+(if (fboundp 'igc-info)
+    (push 'igc features))
 
 ;; The `native-compile' feature exists whether or not it is functional (e.g.
 ;; libgcc is available or not). This seems silly, as some packages will blindly

lisp/packages.el

@@ -7,8 +7,9 @@
 (package! compat
   :recipe (:host github :repo "emacs-compat/compat")
   :pin "38df650dce9f862c6b523de5b683573df590ab85")
-(package! gcmh
-  :pin "0089f9c3a6d4e9a310d0791cf6fa8f35642ecfd9")
+(unless (featurep 'igc)
+  (package! gcmh
+    :pin "0089f9c3a6d4e9a310d0791cf6fa8f35642ecfd9"))
 
 ;; doom-packages.el
 (package! straight