cmake: write xtensor.hpp to local dir to keep global build dir clean#2857

JohanMabille merged 1 commit intoxtensor-stack:masterxtensor-stack/xtensor:masterfrom

jarkkokoivikko-code-q:write-xtensor_hpp-to-local-dirjarkkokoivikko-code-q/xtensor:write-xtensor_hpp-to-local-dirCopy head branch name to clipboard