zsh: move env variables setting before oh-my-zsh

Fixes #207.

modules/programs/zsh.nix

@@ -301,6 +301,10 @@ in
           "source ${pkgs.zsh-autosuggestions}/share/zsh-autosuggestions/zsh-autosuggestions.zsh"
         }
 
+        # Environment variables
+        . "$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh"
+        ${envVarsStr}
+
         ${optionalString cfg.oh-my-zsh.enable ''
             # oh-my-zsh configuration generated by NixOS
             ${optionalString (cfg.oh-my-zsh.plugins != [])
@@ -331,10 +335,6 @@ in
 
         ${cfg.initExtra}
 
-        # Environment variables
-        . "$HOME/.nix-profile/etc/profile.d/hm-session-vars.sh"
-        ${envVarsStr}
-
         # Aliases
         ${aliasesStr}
       '';