tools-related autotests hang on Windows in CI

Since approx. 2nd June, autotests on Windows which use QProcess to test some Qt tool have a greatly increased rate of hanging.

The affected tests include at least:

• tst_moc - http://testresults.qt-project.org/ci/QtBase_master_Integration/build_03009/win32-msvc2010_developer-build_qtnamespace_Windows_7/log.txt.gz
• tst_qmake - http://testresults.qt-project.org/ci/QtBase_master_Integration/build_02997/win32-msvc2010_Windows_7/log.txt.gz
• tst_uic - http://testresults.qt-project.org/ci/QtBase_master_Integration/build_03012/win32-msvc2010_Windows_7/log.txt.gz

It could be a coincidence, or it could be some recent change in qtbase destabilizing QProcess on Windows.