Add -bb to rt.bat to do some extra checks during the tests (it is already used by the non-Windows buildbots).
diff --git a/PCbuild/rt.bat b/PCbuild/rt.bat
index 109d4b6..91b39f7 100644
--- a/PCbuild/rt.bat
+++ b/PCbuild/rt.bat
@@ -40,7 +40,7 @@
PATH %PATH%;..\..\%tcltk%\bin
set exe=%prefix%\python%suffix%
-set cmd=%exe% %dashO% -Wd -E ../lib/test/regrtest.py %1 %2 %3 %4 %5 %6 %7 %8 %9
+set cmd=%exe% %dashO% -Wd -E -bb ../lib/test/regrtest.py %1 %2 %3 %4 %5 %6 %7 %8 %9
if defined qmode goto Qmode
echo Deleting .pyc/.pyo files ...