We remove the 3rdparty dir in build, and we don't need the OpenCL license.

--- opencv-4.1.0/cmake/OpenCVDetectOpenCL.cmake.old	2019-04-07 17:09:10.000000000 +0000
+++ opencv-4.1.0/cmake/OpenCVDetectOpenCL.cmake	2019-07-20 20:21:37.467680107 +0000
@@ -5,7 +5,6 @@
 else()
   set(OPENCL_LIBRARY "" CACHE STRING "OpenCL library")
   set(OPENCL_INCLUDE_DIR "${OpenCV_SOURCE_DIR}/3rdparty/include/opencl/1.2" CACHE PATH "OpenCL include directory")
-  ocv_install_3rdparty_licenses(opencl-headers "${OpenCV_SOURCE_DIR}/3rdparty/include/opencl/LICENSE.txt")
 endif()
 mark_as_advanced(OPENCL_INCLUDE_DIR OPENCL_LIBRARY)