selftests/seccomp: Force rebuild according to dependencies

Rebuild the seccomp tests when kselftest_harness.h is updated.

Signed-off-by: Mickaël Salaün <mic@digikod.net>
Acked-by: Kees Cook <keescook@chromium.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Will Drewry <wad@chromium.org>
Signed-off-by: Shuah Khan <shuahkh@osg.samsung.com>