cmake HAVE___BUILTIN_BSWAP16 examples

GenericMappingTools/gmt cmake/modules/ConfigureChecks.cmake :302

check_c_source_runs (
		"
		int main(void) {
			return !__builtin_bswap16(0xabcd) == 0xcdab;
		}
		"
		HAVE___BUILTIN_BSWAP16)