[$] An update on GCC BPF support

José Marchesi and David Faust kicked off the BPF track at the 2025 Linux Storage,
Filesystem, Memory-Management, and BPF Summit with an extra-long session on what
they have been doing to support compiling to BPF in GCC. Overall, the project is slowly working
toward full support for BPF, with most of the self-tests now passing using
Faust's in-progress patches. However, the progress toward that goal has turned up
a number of problems with how Clang supports BPF that needed to be discussed at
length to find a path forward for both projects.