FindGLEW: select_library_configuration might be used before it is defined

Fixes a regression from !7390 (merged).

Sorry, I missed that with the previous change. The include must have happened somewhere before when I tried it with some "real-world" build rules. The test suite didn't catch it either unfortunately...

See also this report downstream: https://github.com/msys2/MINGW-packages/issues/11932