CentOS 9 Release Detection, master branch (2022.05.16.)
Taught AtlasCMake and AtlasLCG how to parse /etc/os-release in case the lsb_release executable is not available.
This was needed to support CentOS 9, which does not provide lsb_release anymore. As it is described/discussed in ATLINFR-4539 and ADHI-4882.
I made the logic here I believe a little more elegant than what @rhauser did in atlas-tdaq-software/tdaq-common-cmake@e7a91824. With this code if a given system does not provide the lsb_release executable, the code will fall back on looking at the /etc/os-release file if it exists. But the code will still use lsb_release if it's available. I was also able to keep a lot of parsing logic, so that the output parsing for lsb_release and /etc/os-release could be shared. (I also prefer to use just native CMake commands as much as possible. Not requiring the build system to necessarily provide all the shell commands that the TDAQ code uses.)