ocl: added errors processing in OpenCL code generator, resolve space issue

cmake/cl2cpp.cmake

@@ -1,6 +1,14 @@
+if (NOT EXISTS "${CL_DIR}")
+  message(FATAL_ERROR "Specified wrong OpenCL kernels directory: ${CL_DIR}")
+endif()
+
 file(GLOB cl_list "${CL_DIR}/*.cl" )
 list(SORT cl_list)
 
+if (NOT cl_list)
+  message(FATAL_ERROR "Can't find OpenCL kernels in directory: ${CL_DIR}")
+endif()
+
 string(REPLACE ".cpp" ".hpp" OUTPUT_HPP "${OUTPUT}")
 get_filename_component(OUTPUT_HPP_NAME "${OUTPUT_HPP}" NAME)