Added postFixup step to wrap msmtp to bin path

https://discourse.nixos.org/t/makewrapper-vs-buildinputs/21474

Trying to make the global msmtp available to the program

flake.nix

@@ -77,6 +77,11 @@ rust-project TODO: write shell script for automatically updating `cargoHash`
           meta = meta // {
             description = "Using nextcloud notes to track time usage.";
           };
+
+          postFixup = ''
+            wrapProgram $out/bin/time_tracker \
+              --prefix PATH : "${lib.makeBinPath [ msmtp ]}"
+          '';
         });
       };
       nixosModules.default = { config, ... }: let