[$] An update on BPF generation from GCC

The generation of binary code for the kernel's BPF virtual machine has been
limited to the Clang compiler since the beginning; even developers who
use GCC to build kernels must use Clang to compile to BPF. Work has
been underway for some years on adding a BPF backend to GCC as well; the
developers involved ran a session at the 2024 GNU Tools Cauldron to
provide an update on that project. It would seem that the BPF backend is
close to being ready for production use.