mindustry-server: Fix

pkgs/games/mindustry/default.nix

@@ -191,9 +191,8 @@ stdenv.mkDerivation rec {
     gradle --offline --no-daemon server:dist -Pbuildversion=${buildVersion}
   '';
 
-  installPhase = with lib; ''
-    runHook preInstall
-  '' + optionalString enableClient ''
+  installPhase = with lib; let
+    installClient = ''
       install -Dm644 desktop/build/libs/Mindustry.jar $out/share/mindustry.jar
       mkdir -p $out/bin
       makeWrapper ${jdk}/bin/java $out/bin/mindustry \
@@ -215,12 +214,18 @@ stdenv.mkDerivation rec {
       done
 
       install -Dm644 core/assets/icons/icon_64.png $out/share/icons/hicolor/64x64/apps/mindustry.png
-  '' + optionalString enableServer ''
+    '';
+    installServer = ''
       install -Dm644 server/build/libs/server-release.jar $out/share/mindustry-server.jar
       mkdir -p $out/bin
       makeWrapper ${jdk}/bin/java $out/bin/mindustry-server \
         --add-flags "-jar $out/share/mindustry-server.jar"
-  '' + ''
+    '';
+  in ''
+    runHook preInstall
+  '' + optionalString enableClient installClient
+     + optionalString enableServer installServer
+     + ''
     runHook postInstall
   '';