Add Linux game server fallback packaging

Docs/Ops/DedicatedServerBuildRunbook.md

@@ -60,9 +60,31 @@ Expected output:
 - Logs: `Saved\BuildLogs\BuildLinuxDedicatedServer.log`
 - Archive: `Builds\LinuxServerDevelopment`
 
-If the script fails before compile with a Linux toolchain error, install Epic's
-Unreal `5.7` Linux cross-compile toolchain on Windows-Builder, reopen the
-terminal, and run the script again.
+The script self-heals `LINUX_MULTIARCH_ROOT` when the known UE 5.7 toolchain is
+installed at `C:\UnrealToolchains\v26_clang-20.1.8-rockylinux8`.
+
+If the script fails with:
+
+```text
+Server targets are not currently supported from this engine distribution.
+```
+
+the installed Epic binary engine cannot build the true `AgrarianGameServer`
+target. Use the MVP fallback package until a source-built/server-capable engine
+is available:
+
+```bat
+cd /d P:\AgrarianGameBulid
+Scripts\PackageLinuxGameServerFallback-Windows.bat
+```
+
+Fallback expected output:
+
+- Logs: `Saved\BuildLogs\PackageLinuxGameServerFallback.log`
+- Archive: `Builds\LinuxGameDevelopment`
+
+Deploy the fallback package to `/opt/agrarian/server` and launch it through
+`AgrarianGameServer.sh` with `-server -port=7777 -NullRHI -nosound`.
 
 ## Initial Runtime Shape
 

Scripts/BuildLinuxDedicatedServer-Windows.bat

@@ -10,10 +10,17 @@ set "ARCHIVE_DIR=%PROJECT_DIR%\Builds\LinuxServerDevelopment"
 set "LOG_DIR=%PROJECT_DIR%\Saved\BuildLogs"
 set "LOG_FILE=%LOG_DIR%\BuildLinuxDedicatedServer.log"
 set "TARGET_MAP=/Game/Agrarian/Maps/L_GroundZeroTerrain_Test"
+set "DEFAULT_LINUX_MULTIARCH_ROOT=C:\UnrealToolchains\v26_clang-20.1.8-rockylinux8"
 
 if not exist "%LOG_DIR%" mkdir "%LOG_DIR%"
 if not exist "%ARCHIVE_DIR%" mkdir "%ARCHIVE_DIR%"
 
+if "%LINUX_MULTIARCH_ROOT%"=="" (
+  if exist "%DEFAULT_LINUX_MULTIARCH_ROOT%\x86_64-unknown-linux-gnu\bin\clang++.exe" (
+    set "LINUX_MULTIARCH_ROOT=%DEFAULT_LINUX_MULTIARCH_ROOT%"
+  )
+)
+
 if not exist "%BUILD_BAT%" (
   echo Unreal Engine 5.7 Build.bat was not found at:
   echo %BUILD_BAT%
@@ -37,6 +44,7 @@ echo Archive: %ARCHIVE_DIR%
 echo Log: %LOG_FILE%
 echo.
 echo This requires Epic's Linux cross-compile toolchain for Unreal 5.7 on Windows-Builder.
+echo LINUX_MULTIARCH_ROOT=%LINUX_MULTIARCH_ROOT%
 echo.
 
 call "%BUILD_BAT%" AgrarianGameServer Linux Development -Project="%PROJECT_FILE%" -WaitMutex -NoUBA > "%LOG_FILE%" 2>&1

Scripts/PackageLinuxGameServerFallback-Windows.bat

@@ -0,0 +1,76 @@
+@echo off
+setlocal
+
+set "PROJECT_DIR=%~dp0.."
+set "PROJECT_FILE=%PROJECT_DIR%\AgrarianGame.uproject"
+set "UE_ROOT=C:\Program Files\Epic Games\UE_5.7"
+set "RUN_UAT=%UE_ROOT%\Engine\Build\BatchFiles\RunUAT.bat"
+set "ARCHIVE_DIR=%PROJECT_DIR%\Builds\LinuxGameDevelopment"
+set "LOG_DIR=%PROJECT_DIR%\Saved\BuildLogs"
+set "LOG_FILE=%LOG_DIR%\PackageLinuxGameServerFallback.log"
+set "TARGET_MAP=/Game/Agrarian/Maps/L_GroundZeroTerrain_Test"
+set "DEFAULT_LINUX_MULTIARCH_ROOT=C:\UnrealToolchains\v26_clang-20.1.8-rockylinux8"
+
+if not exist "%LOG_DIR%" mkdir "%LOG_DIR%"
+if not exist "%ARCHIVE_DIR%" mkdir "%ARCHIVE_DIR%"
+
+if "%LINUX_MULTIARCH_ROOT%"=="" (
+  if exist "%DEFAULT_LINUX_MULTIARCH_ROOT%\x86_64-unknown-linux-gnu\bin\clang++.exe" (
+    set "LINUX_MULTIARCH_ROOT=%DEFAULT_LINUX_MULTIARCH_ROOT%"
+  )
+)
+
+if not exist "%RUN_UAT%" (
+  echo Unreal Engine 5.7 RunUAT was not found at:
+  echo %RUN_UAT%
+  exit /b 1
+)
+
+if not exist "%PROJECT_FILE%" (
+  echo Project file was not found at:
+  echo %PROJECT_FILE%
+  exit /b 1
+)
+
+if "%LINUX_MULTIARCH_ROOT%"=="" (
+  echo LINUX_MULTIARCH_ROOT is not set and the default toolchain was not found:
+  echo %DEFAULT_LINUX_MULTIARCH_ROOT%
+  exit /b 1
+)
+
+echo Packaging Agrarian Linux game-server fallback...
+echo Archive: %ARCHIVE_DIR%
+echo Log: %LOG_FILE%
+echo LINUX_MULTIARCH_ROOT=%LINUX_MULTIARCH_ROOT%
+echo.
+
+call "%RUN_UAT%" BuildCookRun ^
+  -project="%PROJECT_FILE%" ^
+  -noP4 ^
+  -platform=Linux ^
+  -clientconfig=Development ^
+  -build ^
+  -cook ^
+  -stage ^
+  -pak ^
+  -archive ^
+  -archivedirectory="%ARCHIVE_DIR%" ^
+  -map=%TARGET_MAP% ^
+  -utf8output ^
+  -NoUBA > "%LOG_FILE%" 2>&1
+
+set "PACKAGE_EXIT_CODE=%ERRORLEVEL%"
+type "%LOG_FILE%"
+
+if not "%PACKAGE_EXIT_CODE%"=="0" (
+  echo.
+  echo Linux game-server fallback package failed with exit code %PACKAGE_EXIT_CODE%.
+  echo Log file: %LOG_FILE%
+  exit /b %PACKAGE_EXIT_CODE%
+)
+
+echo.
+echo Linux game-server fallback package completed successfully.
+echo Archive: %ARCHIVE_DIR%
+echo.
+exit /b 0