use buildEnv instead of joinsymlinks

buildEnv respects propagatedUserEnvPkgs

lib.nix

@@ -23,10 +23,4 @@
   pkgs-by-name = callPackage: dir:
     lib.mapAttrs (pkg: _: callPackage (dir + "/${pkg}/package.nix") {})
     (lib.filterAttrs (_: type: type == "directory") (builtins.readDir dir));
-
-  buildEnvMpi = symlinkJoin: input:
-    symlinkJoin {
-      inherit (input) name;
-      paths = lib.flatten (map(x: if x ? passthru.mpi then [ x x.passthru.mpi ] else x) input.paths);
-    };
 }

overlay.nix

@@ -39,7 +39,6 @@ let
 
         inherit callPackage;
         inherit aggressiveStdenv;
-        inherit qlib;
 
         #
         # Upstream overrides

template/qc/nix/flake.nix

@@ -72,7 +72,7 @@
       # EDITME
       # Add packages to the default package as you wish
       packages."${system}" = (filterDrvs pkgs.qchem) // {
-        default = pkgs.qchem.qlib.buildEnvMpi pkgs.symlinkJoin {
+        default = pkgs.buildEnv {
           name = "quantum-chemistry";
           paths = [
             # put a list of packages here. e.g.: