|I think the problem is "descriptive terminology".
I have a "mother directory" OpenCV with CMakeList.txt file I execute using CMake.
I did not bother to find were CMake resides.
Now CMake wants to know "source directory".
That is why I asked - apparently it is the "mother directory" and not some specific real source code of OpenCV.
( I suppose analyzing CMake would give some clue )
Now CMake will build OpenCV library and again - where should this "build" be?
Logically it belongs under the mother directory just to keep things under common directory.
Apparently, and I do not discount I made some other mistake, that caused the warning.
It all sounds pretty simple, but turns difficult to troubleshoot when things do not go right.
For example CMake finishes the "build" gives no "option" to quit / exit -just ask for same "click this or that again ".
But I am making some progress thanks to this forum.