Reduce build times on Windows

[MarcoAlanen]

Greetings

We are currently having an issue with build times on the Windows platform while the Linux builders can build our project really fast:
Linux: 11m:43s <-- Release
Windows: 57m:37s <-- Debug
Windows: 1h:22m <-- Release

I went through the build log and saw that the moc generation can be extremely slow, especially when it comes to the unit tests. For example:

[01:48:43]: MOC ..\..\PathToTest\TestFile.cpp
[01:48:51]: Compiling...
[01:48:51]: TestFile.cpp

That's a 300 line file using the QTest framework, nothing fancy. Is there any way we can speed up this process or are there some pitfalls we should try to avoid? We're using Qt 4.6.2.

Edit: I found this post which seems to observe the same symptoms but without a solution.

Edit: We tried to disable Windows Defender but it had no impact on the build time.