Should CET be enabled by default in GCC8

[Uros Bizjak]

Hello!

Currently, CET is enabled by default for linux if target supports
multi-byte NOPs and if assembler supports CET insn. Effectively, with
newer binutils, CET support is an opt-out feature.

I don't think this should be the case, and I propose to consider CET
as an opt-in feature. Multi-byte NOPs have non-zero cost (at least
they increase the binary). If someone wants to enable the feature, it
can be done in less surprising way to --enable-cet during configure
time.

I'd like to hear the opinion of RMs, if CET should remain to be an
opt-out feature by default?

Uros.