Re: 2026Q1 and USE_CXX_FEATURES+=c++20

EF> compiler/gcc.mk says:
EF> # gcc documents that 11 is required, with a few perhaps-obscure
EF> # features requiring 12.  gcc10 does not define __cplusplus as meeting
EF> # c++20.

gdt> If you think that isn't accurate, please cite upstream docs.
I wasn't questioning that, I just wanted to illustrate why 
USE_CXX_FEATURES+=c++20 inflicts gcc12 on me.

> Our unwillingness to slice a standard into dozens of parts and expend
> lots of effort to validate which gcc versions support which subsets
> and try to avoid requiring new gcc.
Given most upstreams will probably respond "update to trixie!" or 
"why don't you use our docker container?", what would help is something 
like USE_CXX_FEATURES+= formally-c++12-but-c++17-from-gcc10-works.
Of course no-one will want to go down that rabbit hole, so I'll continue 
to patch locally.