tests: change blackbox test to work cross platform
While it is not easy to make a file 000 on Windows, you can
emulate most of the behaviors by replacing the file with a directory.
Also corrects test description to properly indicate that failing to
read from the log is fatal.
<Include>
<?if $(var.Platform) = "x64" ?>
<?define IsX64 = yes ?>
<?else?>
<?define IsX64 = no ?>
<?endif?>
</Include>