Add missing OCL_TUNE define to CMake build

      add_library(gpu STATIC ${GPU_LIB_SOURCES})

      target_link_libraries(gpu ${OpenCL_LIBRARIES})

      target_include_directories(gpu PRIVATE ${CMAKE_CURRENT_BINARY_DIR}/gpu ${OpenCL_INCLUDE_DIRS})

      target_compile_definitions(gpu PRIVATE -D_${GPU_PREC} -DMPI_GERYON -DUCL_NO_EXIT)

      target_compile_definitions(gpu PRIVATE -D_${GPU_PREC} -D${OCL_TUNE}_OCL -DMPI_GERYON -DUCL_NO_EXIT)

      target_compile_definitions(gpu PRIVATE -DUSE_OPENCL)

      list(APPEND LAMMPS_LINK_LIBS gpu)