minijail: add seccomp softfail option

Minijail now softfails when seccomp is not implemented
by the OS. However if the USE_seccomp flag is defined,
minijail still hardfails.

BUG=chromium:368071
TEST=Manual: compiled with and without USE flag.
CQ-DEPEND=CL:212960

Change-Id: If2b58ddd5ce51a357bda325d32fe2b3dac6df11f
Reviewed-on: https://chromium-review.googlesource.com/212919
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Tested-by: Utkarsh Sanghi <usanghi@chromium.org>
Commit-Queue: Utkarsh Sanghi <usanghi@chromium.org>
2 files changed