Fix predicate testing if git is needed

[nocnokneo]

The uses the same predicate in the current MITK/SuperBuild.cmake

[saschazelzer]

Thanks for the pull request. You are using the same expression as in the MITK project, however some CMake variable do not actually make sense in this context.

Could you please describe the problems you run into in the first place?

[nocnokneo]

Sorry for the slow response. I can't quite remember the exact problem I was having. I went back to try and re-produce it, but can't now. IIRC it was the BUILD_TESTING check that was the key part (we building with testing disabled).

[saschazelzer]

Thanks for the feedback. I also tried to reproduce a failure with various configuration options but couldn't. I would suggest to close the pull request and re-open it if you run into similar problems again.

[nocnokneo]

Sounds good. Closed for now.