Included below is a patch for SBCL (under FreeBSD) to use
linux-stubs.S instead of the C stubs in bsd-os.c. This works fine for
FreeBSD, and should hopefully also work for OpenBSD as soon as dynamic
linking works on that platform.
Speaking of which: It's possible that the command line options
"-Xlinker --export-dynamic" (in that order) will achieve the same
effect as just "--export-dynamic" does under FreeBSD. I suspect that
the latter has been added to the gcc driver program in later versions
of gcc, or just to the version shipped with FreeBSD.