> That must be me, so I will take a look now. I think it's because
> I didn't build with --enable-targets=all.

Attached is the patch I just pushed to master.

gdb/ChangeLog:

        * amd64-darwin-tdep.c (x86_darwin_init_abi_64): Add missing
        parameter in call to amd64_target_description.
        * amd64-dicos-tdep.c (amd64_dicos_init_abi): Likewise.
        * amd64-fbsd-tdep.c (amd64fbsd_core_read_description)
        (amd64fbsd_init_abi): Likewise.
        * amd64-nbsd-tdep.c (amd64nbsd_init_abi): Likewise.
        * amd64-obsd-tdep.c (amd64obsd_init_abi): Likewise.
        * amd64-sol2-tdep.c (amd64_sol2_init_abi): Likewise.
        * amd64-fbsd-nat.c (amd64_fbsd_nat_target): Likewise.

The change to amd64-fbsd-nat.c was done "blind" (no access to system),
but is reasonably straightforward. The changes to the -tdep.c files
were verify by rebuilding GDB on x86_64-linux when configured with
--enable-targets=all.

-- 
Joel