pseudo: Force seccomp to return success when in fact doing nothing

Pseudo changes the syscall access patterns which makes it incompatible with
seccomp. Therefore intercept the seccomp syscall and alter it, pretending that
seccomp was setup when in fact we do nothing. If we error as unsupported,
utilities like file will exit with errors so we can't just disable it.

This works around issues on platforms where seccomp is enabled in file
(e.g. archlinux).

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>