zsh: Explicitly disable prompt in user config

Otherwise starship does not work in 21.05.

users/simon/modules/zsh.nix

@@ -64,17 +64,22 @@ in
       envExtra = ''
         export _JAVA_OPTIONS="-Dawt.useSystemAAFontSettings=on"
       '';
-      initExtra = lib.mkAfter ''
-        eval $(${pkgs.coreutils}/bin/dircolors -b ${dircolors-solarized}/dircolors.ansi-universal)
+      initExtra = lib.mkMerge [
+        (lib.mkBefore ''
+          prompt off # collides with starship
+        '')
+        (lib.mkAfter ''
+          eval $(${pkgs.coreutils}/bin/dircolors -b ${dircolors-solarized}/dircolors.ansi-universal)
 
-        # no sad smiley (starship shows exit status)
-        zstyle ':prompt:grml:right:setup' items
+          # no sad smiley (starship shows exit status)
+          zstyle ':prompt:grml:right:setup' items
 
-        # do not glob # (conflicts with nix flakes)
-        disable -p '#'
+          # do not glob # (conflicts with nix flakes)
+          disable -p '#'
 
-        source ${../files/zsh/pass-wrappers.zsh}
-      '';
+          source ${../files/zsh/pass-wrappers.zsh}
+        '')
+      ];
     };
   };
 }