apt: Disable libseccomp

This isn't in DEPENDS and isn't configured. It can detect the library when
pulled in via other dependencies meaning the build isn't deterministic.

Ultimately this could become a PACKAGECONFIG. It doesn't build on musl
so disable it for now until someone fixes and sorts this out properly.

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