System information (version)

• OpenCV => 3.4
• Operating System / Platform => Mac

Detailed description

I try to build OpenCV for Android by my own on my Mac, inspired by this log I installed the exact NDK android-ndk-r10e

and I was forced to install ninja by brew install ninja
but currently I see

CMake Error: CMake was unable to find a build program corresponding to "Ninja". CMAKE_MAKE_PROGRAM is not set

But I need some explanation for
buildenv python ../opencv/platforms/android/build_sdk.py --build_doc --extra_pack 2.4.13:/opt/android/pack_2.4/ . ../opencv

What is

• buildenv how does it looks like ?
• --extra_pack what is the content of /opt/android/pack_2.4/ ?
• how to get rid of CMAKE_MAKE_PROGRAM is not set ?