Restore GLEW include

[sarlinpe]

Since #2176, building with CUDA_ENABLED=ON GUI_ENABLED=OFF fails due to undfined GL_* symbols:

colmap/src/colmap/feature/sift.cc

Lines 652 to 656 in e701436

	const int code = sift_gpu_.RunSIFT(bitmap.ScanWidth(),
	bitmap.Height(),
	bitmap_raw_bits.data(),
	GL_LUMINANCE,
	GL_UNSIGNED_BYTE);

[ahojnnes]

Oh man, thanks. It could be good to have one of the two cuda builds disable the GUI to catch this in CI? Probably the older 20.04 one.

[sarlinpe]

Yes!