fix msvc build with glut
This fixes the MSVC build if GLUT is somehow found. See !139 (merged) for a way of making that happen, but it can be done manually with enough fiddling as well, so it's probably worth fixing regardless.
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This fixes the MSVC build if GLUT is somehow found. See !139 (merged) for a way of making that happen, but it can be done manually with enough fiddling as well, so it's probably worth fixing regardless.