There is no known (real) hardware with V and without the complete B
extension. B was indeed required in the RISC-V application profile from
2022, earlier than V. There should not be any relevant hardware in the
future either.
In practice, different R-V Vector optimisations in FFmpeg already depend on
every constituent of the B extension anyhow, so it would not work well.
Otherwise aacenc.o gets pulled in by the aacencdsp checkasm
test and it in turn pulls the rest of lavc in.
Besides being bad size-wise this also has the downside that
it pulls in avpriv_(cga|vga16)_font from libavutil which are
marked as being imported from another library when building
libavcodec as a DLL and this breaks checkasm because it links
both lavc and lavu statically.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
