c++20: require gcc12?

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

In mk/compiler/gcc.mk we have:

.if !empty(USE_CXX_FEATURES:Mc++20)
# gcc documents that 11 is required, with a few perhaps-obscure
# features requiring 12.

# 10 is the version included in netbsd-10.
# We hope that it remains OK for most C++20 in the future...
GCC_REQD+=      10
.endif


finance/bitcoin requires c++20, and in
http://www.ki.nu/pkgsrc/reports/current/NetBSD-9.0/20250207.2153/bitcoin-28.1/configure.log
pulls in a gcc10 package, but the configure script is not happy:

checking whether c++ supports C++20 features with -std=c++20... no
checking whether c++ supports C++20 features with +std=c++20... no
checking whether c++ supports C++20 features with -h std=c++20... no
configure: error: *** A compiler with support for C++20 language features is required.

So I think we should bump the requirement to gcc 12.

Comments?
 Thomas