emacsPackages.age: replace program (#343569)

pkgs/applications/editors/emacs/elisp-packages/melpa-packages.nix

@@ -133,6 +133,13 @@ let
         # Expects bash to be at /bin/bash
         ac-rtags = fix-rtags super.ac-rtags;
 
+        age = super.age.overrideAttrs (attrs: {
+          postPatch = attrs.postPatch or "" + ''
+            substituteInPlace age.el \
+              --replace-fail 'age-program (executable-find "age")' 'age-program "${lib.getExe pkgs.age}"'
+          '';
+        });
+
         airline-themes = super.airline-themes.override {
           inherit (self.melpaPackages) powerline;
         };