Fix blackbox tests.

There were false negatives on Unix systems due to the use of
QFile::exists() on paths supposed to be executable files. We now
explicitly check whether the path refers to a file as to not
inadvertantly match directories anymore.

Change-Id: I3023fb0b9452f5cf3fbf1f2d678a4291cac75e42
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>
Fix MSVC working directory.

The directory for object files has changed.

Change-Id: I78109ccfd2a23aedb2cd5a57ef689099d621e485
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>