Remove compatibility with CMake versions older than 2.8.0

This compatibility has been deprecated since commit 5845c218d7
(Deprecate compatibility with CMake versions older than 2.8.12,
2020-06-12, v3.19.0-rc1~629^2).  The behavior itself has been
deprecated since CMake 2.8.0.

Issue: #26613
20 files changed