Set a proxy environment variable EMACS_SNAP_DIR for SNAP_ARCH

We unset $SNAP in site-start.el so that any other snaps that get run as child
processes by emacs don't get confused so make sure we can preserve and still
refer to this via the name EMACS_SNAP_DIR

Signed-off-by: Alex Murray <[email protected]>

site-lisp/site-start.el

@@ -19,13 +19,15 @@
                "FONTCONFIG_FILE"))
   (setenv env))
 
-;; ensure the correct native-comp-driver-options are set - use
-;; /snap/emacs/current if $SNAP is not set for some reason - we also patch
+;; keep a proxy to the SNAP env so that our patched comp.el and treesit.el can
+;; use it - use /snap/emacs/current if $SNAP is not set for some reason
+(setenv "EMACS_SNAP_DIR" (or (getenv "SNAP") "/snap/emacs/current"))
+
+;; ensure the correct native-comp-driver-options are set -- we also patch
 ;; comp.el in when building the emacs snap but do it here too to try and
 ;; ensure this is always set no matter what
 (when (require 'comp nil t)
-  (let ((sysroot (file-name-as-directory (or (getenv "SNAP")
-                                             "/snap/emacs/current"))))
+  (let ((sysroot (file-name-as-directory (getenv "EMACS_SNAP_DIR"))))
     (dolist (opt (list (concat "--sysroot=" sysroot)
                        (concat "-B" sysroot "usr/lib/gcc/")))
       (add-to-list 'native-comp-driver-options opt t))))

treesit.patch

@@ -7,12 +7,12 @@ index e718ea1a23a..3a313c613ee 100644
           (workdir (expand-file-name "repo"))
           (source-dir (expand-file-name (or source-dir "src") workdir))
 -         (cc (or cc (seq-find #'executable-find '("cc" "gcc" "c99"))
-+         (cc (or cc (concat (file-name-as-directory (getenv "SNAP")) "usr/bin/gcc-10")
++         (cc (or cc (concat (file-name-as-directory (getenv "EMACS_SNAP_DIR")) "usr/bin/gcc-10")
                   ;; If no C compiler found, just use cc and let
                   ;; `call-process' signal the error.
                   "cc"))
 -         (c++ (or c++ (seq-find #'executable-find '("c++" "g++"))
-+         (c++ (or c++ (concat (file-name-as-directory (getenv "SNAP")) "usr/bin/g++-10")
++         (c++ (or c++ (concat (file-name-as-directory (getenv "EMACS_SNAP_DIR")) "usr/bin/g++-10")
                    "c++"))
           (soext (or (car dynamic-library-suffixes)
                      (signal 'treesit-error '("Emacs cannot figure out the file extension for dynamic libraries for this system, because `dynamic-library-suffixes' is nil"))))