Restore depot_tools autoupdate in Windows.

Original CL:

Executing a bat file from another bat file will replace
that first bat file with the second one. To call the
second one and then return and execute the rest of the
first one, you have to do "call second.bat"

"python" is really "python.bat" so that this happened
was not obvious. More obvious now.

Review URL: .

git-svn-id: svn:// 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/update_depot_tools.bat b/update_depot_tools.bat
index 84b0a1f..983a29e 100644
--- a/update_depot_tools.bat
+++ b/update_depot_tools.bat
@@ -29,7 +29,7 @@

 :: Initialize/update virtualenv.

 cd /d "%DEPOT_TOOLS_DIR%."

-python -u bootstrap\ --deps_file bootstrap\deps.pyl --quiet ENV

+call python.bat -u bootstrap\ --deps_file bootstrap\deps.pyl --quiet ENV

 if errorlevel 1 goto :EOF


 :: Shall skip automatic update?