There were many occasions where talk was of us raising the baseline of e.g. the compiler, assembler, and linker we use for building Xen and/or the tool chain. Clear criteria for how to select such a baseline were never established, resulting in largely random suggestions. One goal here would be to establish such criteria, ideally allowing to finally raise the baseline in 4.18.
Things aren’t limited to tool chain components, though. Various other tools (Perl, Python, and even basic utilities) are also used for building our code and, as dependencies, for running tool chain components. Further runtime dependencies are of course (system) libraries. While the tool chain part of the build system leverages the commonly used configure approach, the question for all of these dependencies still is: What base level of functionality do we require (lack thereof then e.g. causing configure to fail)? My general view here is that basic functionality should be available on even fairly old systems, whereas advanced functionality may have more modern prerequisites. Likely others view this differently, and hence reaching some form of consensus would be another goal here.