README.cmake.md: Add new documentation for CMake buildsystem

README.cmake.md: Add new documentation for CMake buildsystem

While here, adapt and update some of the Windows-build
references in the other README files.

Change-Id: Id067774bde7511a736e156fc599b07837242336c
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20230707150523.385264-1-frank@lichtenheld.com>
URL: https://www.mail-archive.com/search?l=mid&q=20230707150523.385264-1-frank@lichtenheld.com
Signed-off-by: Gert Doering <gert@greenie.muc.de>