Export now no cinema image database on windows source builds

Tested with 5.7.0-RC1 binary on Windows 10 and source build from release branch

I cannot export a cinema image database with export now on windows.

To recreate:

1. Create a wavelet source and show the surface colored by RTData
2. View -> Export Inspector
3. Choose Cinema Image Database for the image extract and check the box
4. Set a writable root directory
5. Check the save cinema D table box
6. File -> Export Now

I don't get anything. The root directory is not even created.