mx-sanebot: allow building zeal docs

pkgs/mx-sanebot/default.nix

@@ -14,6 +14,10 @@ rustPlatform.buildRustPackage {
   nativeBuildInputs = [ pkg-config ] ++ lib.optional (cargo-docset != null) cargo-docset;
   buildInputs = [ openssl ];
 
+  # to build dash/zeal docs:
+  # `cargo-docset`
+  # `cp -r -rcp target/docset/mx-sanebot.docset ~/.local/share/Zeal/Zeal/docsets/`
+
   # enables debug builds, if we want: https://github.com/NixOS/nixpkgs/issues/60919.
   hardeningDisable = [ "fortify" ];
 }

pkgs/mx-sanebot/shell.nix

@@ -1,4 +1,6 @@
-{ pkgs ? import <nixpkgs> {} }:
+{ pkgs ? import <nixpkgs> {
+  overlays = [ (import ../../overlays/pkgs.nix) ]; }
+}:
 
 let
   mx-sanebot = pkgs.callPackage ./. { };
@@ -9,5 +11,5 @@ in
     ];
 
     # Allow cargo to download crates.
-    SSL_CERT_FILE = "${cacert}/etc/ssl/certs/ca-bundle.crt";
+    SSL_CERT_FILE = "${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt";
   }