Merged PR 669257: Don't use the NuGet cache when downloading the BuildXL LKG on local builds

NuGet uses a shared non-deduplicated cache by default. On local machines this results in a lot of space taken by stale bxl LKGs. Skip the cache for this case to save on disk space. The only scenario that a shared cache could be helping with in this case is if a developer has multiple bxl enlistments, but this case is not super common, and it will only save download time (not space).

Shared/Scripts/Init.cmd

@@ -91,14 +91,23 @@ REM *********************************
 
 	set _BUILDXL_BOOTSTRAP_OUT=%ENLISTMENTROOT%\Out\BootStrap
 
+	SETLOCAL
+
+	REM If not on ADO, don't use the NuGet cache when downloading the LKG
+	if "%TF_BUILD%" == "" (
+		set DIRECTDOWNLOAD="-DirectDownload"
+	)
+
 	REM use nuget to pull the current LKG down
 	echo BUILDXL-Init: Using nuget to Pull package '%BUILDXL_LKG_NAME%' version '%BUILDXL_LKG_VERSION%'
-	%TOOLROOT%\nuget.exe install -OutputDirectory %_BUILDXL_BOOTSTRAP_OUT% -Source %BUILDXL_LKG_FEED_1% %BUILDXL_LKG_NAME% -Version %BUILDXL_LKG_VERSION% %BUILDXL_NUGET_WORKAROUNDS%
+	%TOOLROOT%\nuget.exe install %DIRECTDOWNLOAD% -OutputDirectory %_BUILDXL_BOOTSTRAP_OUT% -Source %BUILDXL_LKG_FEED_1% %BUILDXL_LKG_NAME% -Version %BUILDXL_LKG_VERSION% %BUILDXL_NUGET_WORKAROUNDS%
 	if ERRORLEVEL 1 (
 		echo ERROR: Failed to pull nuget package
 		exit /b 1
 	)
 
+	ENDLOCAL
+
 	goto :EOF
 
 REM *********************************