opencv用mingw64在Windows系统中编译出现的问题
opencv（V3.4.7）
mingw64（MinGW-W64 GCC-8.1.0_x86_64-8.1.0）
Windows10 Professional 64bit
错误描述：
‘chmod’不是内部或外部命令，也不是可运行的程序 或批处理文件 | ‘chmod’ is not recognized as an internal or external command

解决方法：https://github.com/opencv/opencv/pull/15433/files

${_command} '-D$<JOIN:$<TARGET_PROPERTY:${_targetName},COMPILE_DEFINITIONS>,' '-D>'
")GET_FILENAME_COMPONENT(_outdir ${_output} PATH)if(NOT CMAKE_HOST_WIN32)  # chmod may be not available on Win32/MinGW (and it is not required)set(_pch_prepare_command COMMAND chmod +x "${_pch_generate_file_cmd}")endif()ADD_CUSTOM_COMMAND(OUTPUT "${_output}"COMMAND ${CMAKE_COMMAND} -E make_directory "${_outdir}"COMMAND chmod +x "${_pch_generate_file_cmd}"${_pch_prepare_command}COMMAND "${_pch_generate_file_cmd}"DEPENDS "${_input}" "${_pch_generate_file_cmd}"DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/${_name}"