Mainly caused by moving tests to source folder, which brings
new compiler flags.
Also, no need to extend include directories (to the non-existing paths,
btw) since this is done by the CmakeList.txt which is in the blenlib folder.
And make them part of the blender_test runner. The one exception is blenlib
performance tests, which we don't want to run by default. They remain in their
own executable.
Differential Revision: https://developer.blender.org/D8498
