ocl: force to use Khronos OpenCL headers

cmake/checks/opencl.cpp

@@ -0,0 +1,15 @@
+#if defined __APPLE__
+#include <OpenCL/cl.h>
+#else
+#include <CL/cl.h>
+#endif
+
+int main(int argc, char** argv)
+{
+#ifdef CL_VERSION_1_2
+#error OpenCL is valid
+#else
+#error OpenCL check failed
+#endif
+    return 0;
+}