Cmake error at
opencv_contrib-master/modules/datasets/CMakeLists.txt:5 (ocv_append_source_files_cxx_compiler_options):
Unknown CMake command "ocv_append_source_files_cxx_compiler_options".

-- Configuring incomplete, errors occurred!
See also "/home/sunhong/Downloads/opencv-3.4.1/my_build_dir/CMakeFiles/CMakeOutput.log".

See also "/home/sunhong/Downloads/opencv-3.4.1/my_build_dir/CMakeFiles/CMakeError.log".

解决方法：

1.注释掉:opencv_contrib-master/modules/datasets/CMakeLists.txt:5 (ocv_append_source_files_cxx_compiler_options):

2.

～\opencv_contrib\modules\dnn_modern\CMakeLists.txt
20行改为
ocv_download(PACKAGE "v1.0.0a3.tar.gz"

～\opencv_contrib\modules\xfeatures2d\cmake\download_boostdesc.cmake
22行改为
 ocv_download(PACKAGE ${name_${id}}

～\opencv_contrib\modules\xfeatures2d\cmake\download_vgg.cmake
16行改为
ocv_download(PACKAGE ${name_${id}}

3.ippicv包的问题：由于网络原因