When Qt commercial installer command prompt is opened (Qt Commercial 5.0.1 for Desktop (MSVC 2010)), this message is displayed:
Remember to call vcvarsall.bat to complete environment setup!
In 4.8 installers, vcvarsall.bat was called automatically.
If you only have the Windows SDK (v7.0 or v7.1) and no Visual Studio Installed, vcvarsall.bat is not available. Instead you are supposed to use SetEnv.cmd (Usually located in C:\Program Files\Microsoft SDKs\Windows\v7.1\Bin)
This also worked in 4.8