linux: Enable seccomp filter on ARM

linux: Enable seccomp filter on ARM

Since last time we checked, the kernel's security features on ARM have
improved notably (see CONFIG_RANDOMIZE_BASE discussion). This patch
therefore proposes to give the seccomp filter on both 32- and 64-bit ARM
another try, since it provides significant security benefit to
applications using it.

Due to operational constraints, rootfile changes have been omitted, and
will be conducted, should this patch be approved.

Note to future self: Once this patch is approved, applications using
seccomp (OpenSSH, Tor) need to be updated/shipped on ARM.

Fixes: #12366
Fixes: #12370
Cc: Arne Fitzenreiter <arne.fitzenreiter@ipfire.org>
Signed-off-by: Peter Müller <peter.mueller@ipfire.org>