epiphany: fix to launch on moby

hosts/common/programs/epiphany.nix

@@ -1,6 +1,27 @@
-{ ... }:
+# epiphany web browser
+# - GTK4/webkitgtk
+#
+# usability notes:
+# - touch-based scroll works well (for moby)
+# - URL bar constantly resets cursor to the start of the line as i type
+#   - maybe due to the URLbar suggestions getting in the way
+{ pkgs, ... }:
 {
   sane.programs.epiphany = {
+    # XXX(2023/07/08): running on moby without this hack fails, with:
+    # - `bwrap: Can't make symlink at /var/run: File exists`
+    # this could be due to:
+    # - epiphany is somewhere following a symlink into /var/run instead of /run
+    #   - (nothing in `env` or in this repo touches /var/run)
+    # - no xdg-desktop-portal is installed  (unlikely)
+    #
+    # a few other users have hit this, in different contexts:
+    # - <https://gitlab.gnome.org/GNOME/gnome-builder/-/issues/1164>
+    # - <https://github.com/flatpak/flatpak/issues/3477>
+    # - <https://github.com/NixOS/nixpkgs/issues/197085>
+    package = pkgs.writeShellScriptBin "epiphany" ''
+      WEBKIT_DISABLE_SANDBOX_THIS_IS_DANGEROUS=1 ${pkgs.epiphany}/bin/epiphany
+    '';
     persist.private = [
       ".cache/epiphany"
       ".local/share/epiphany"