It took a lot of testing and experimentation, but these changes make the qt-win32 gitian build deterministic, and stop the build from randomly hanging on qmake in a loop due to time conflicts.
They also shorten the build time and reduce library size by disabling more qt features such as OpenGL that we don't use.
Hopefully, this is reproducible on other computers as well. The output hashes are:
7996f302a7ea07a7c3728c857ca0ed783dd96fc49898cf149432787b93016ce6 qt-win32-4.7.4-gitian.zip
dbdda19724304cb7006c6bcfe851a4b91f9939f9f282eec24d6768f8070126e7 qt-res.yml