make it compile with cmake.

include/opencl_helper.hpp

@@ -0,0 +1,11 @@
+#ifndef OPENCL_HELPER_H_
+#define OPENCL_HELPER_H_
+
+#include <CL/opencl.hpp>
+
+namespace OpenCL{
+  cl::Device select_devices();
+}
+
+
+#endif // OPENCL_HELPER_H_