On some systems it can error while detecting SDL2, in that case it returns
without calling the failure function, and thus love continues configuring. I'm
hoping it doesn't call the success callback either, so we can instead check
whether it succeeded, and show an error if it didn't.
Theoretically I could enable it on a case-by-case basis, but as of now glslang,
physfs and the thread module all require pthread, so I might as well just
always link it in.