docker/Debian/oldstable: everything built twice, due to implicit "preinstall" target
For each Py minor, the docker/Debian/oldstable takes scandalously long. It goes silent for about ten minutes after the messages
$ time cpack -B ./installer .
CPack: Create package using STGZ
CPack: Install projects
CPack: - Run preinstall target for: BornAgain
From discussions in the web I infer that it spends this time doing a complete rebuild.
This is controlled by the implicit "preinstall" target, which exists only under Make, not under Ninja, see https://discourse.cmake.org/t/cpack-run-preinstall-target/10187/5.
So an easy solution could be: Wait for CMake >= 3.26, then migrate from Make to Ninja. BUT: There is something wrong with our dependencies. We should better fix the root cause, rather then making one of its effects disappear.
Edited by Wuttke, Joachim