Change REQUIRES to PRIV_REQUIRES because the public API of this package does not require users of this package to know about arduino. This can cut down on the compile time & search paths (see https://cmake.org/pipermail/cmake/2016-May/063400.html for more details).
Change
REQUIREStoPRIV_REQUIRESbecause the public API of this package does not require users of this package to know aboutarduino. This can cut down on the compile time & search paths (see https://cmake.org/pipermail/cmake/2016-May/063400.html for more details).