beamPackages.hex: replace bundled CA certs with cacert

Assisted-By: Claude Opus 5.5 low in claude-code/2.1.303

pkgs/development/beam-modules/hex/default.nix

@@ -1,6 +1,7 @@
 {
   lib,
   stdenv,
+  cacert,
   fetchFromGitHub,
   writeText,
   elixir,
@@ -27,6 +28,10 @@ let
         sha256 = "sha256-lOoD6mzctGk9xHNJiribDMVWQ9xrr2N5eluJalirESk=";
       };
 
+      postPatch = ''
+        cp ${cacert}/etc/ssl/certs/ca-bundle.crt lib/hex/http/ca-bundle.crt
+      '';
+
       setupHook = writeText "setupHook.sh" ''
         addToSearchPath ERL_LIBS "$1/lib/erlang/lib/"
       '';