If the bolt ends below the depth of the slot in the nut section, you can remove the crank. stand a screwdriver up in a vise, and push down on the crank to keep the screwdriver in the slot while turning the screw out with a hex key.
OTOH, keep in mind that chainring bolts are pretty damn cheap, and not worth sacrificing tools for. If it persists in it's stubbornness, use a 5/16" drill to drill it through and both halves will come out their respective sides. Then pay the $2.00 and buy a new bolt.
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