emacs: use TERMINAL environment variable

home/default/basic.nix

@@ -6,4 +6,9 @@
   # Home Manager needs a bit of information about you and the paths it should manage.
   home.username = lib.mkDefault "tb";
   home.homeDirectory = lib.mkDefault "/home/${config.home.username}";
+
+  # Set default terminal environment variable
+  home.sessionVariables = {
+    TERMINAL = lib.mkDefault "urxvt";
+  };
 }

home/develop/emacs/custom.el

@@ -951,7 +951,7 @@ frame if FRAME is nil, and to 1 if AMT is nil."
   (interactive)
   (if (file-remote-p default-directory)
       (shell)
-    (start-process "terminal" nil "urxvt")))
+    (start-process "terminal" nil (getenv "TERMINAL"))))
 
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 ;; --- Compilation