Linux: Change the default for seccomp soft-fail.

Make seccomp hard-fail by default, and soft-fail when USE_seccomp is
"no".

This simplifies building on Linux because most folks no longer have to
pass USE_seccomp=yes when building.

Bug: 37162444
Test: Builds with USE_seccomp=yes, with USE_seccomp=no, without.
Test: With USE_seccomp=yes and without produces the same binary.
Change-Id: I3821f5b7d2db78e334107263fed0a591695540a3
1 file changed