labs: protect downloader.js from deletion

In its current location, the download helper for Window batch scripts,
downloader.js, gets deleted when the Windows batch scripts are generated
(due to a call to clean_dir).

This patch moves downloader.js to the tools directory where it remains
safe from clean_dir.

Change-Id: I48f3daf613e8517dfb9256af298e9e43f76289bc

labs/lib/wbatch/template-begin_base_bat

@@ -14,7 +14,7 @@ ECHO.
 ECHO Expect this to take several minutes or longer, depending on your
 ECHO Internet connection.
 ECHO.
-cscript /nologo downloader.js %ISOURL%
+cscript /nologo %TOOLSDIR%\downloader.js %ISOURL%
 RENAME downloaded.bin %INSTALLFILE%
 MOVE %INSTALLFILE% %IMGDIR%
 IF EXIST %IMGDIR%\%INSTALLFILE% goto got_install_iso

labs/lib/wbatch/template-mkdirs_bat

@@ -8,6 +8,7 @@ SET IMGDIR=%TOPDIR%\%P_IMGDIR%
 SET LOGDIR=%TOPDIR%\%P_LOGDIR%
 SET STATUSDIR=%TOPDIR%\%P_STATUSDIR%
 SET SHAREDIR=%TOPDIR%
+SET TOOLSDIR=%TOPDIR%\tools
 
 ECHO %time% Creating directories (if needed)
 IF NOT EXIST %AUTODIR% mkdir %AUTODIR%

labs/tools/downloader.js

@@ -1,5 +1,6 @@
 /* Taken from http://superuser.com/a/536400 */
 /* Use: cscript /nologo downloader.js <URL> */
+/* Used by Windows batch scripts to download distro ISO image */
 
 var WinHttpReq = new ActiveXObject("WinHttp.WinHttpRequest.5.1");
 WinHttpReq.Open("GET", WScript.Arguments(0), /*async=*/false);