[MacPorts] #62677: Add C++20 support for configure.cxx_standard

[MacPorts]

#62677: Add C++20 support for configure.cxx_standard
--------------------------+--------------------
  Reporter:  ryandesign   |      Owner:  (none)
      Type:  enhancement  |     Status:  new
  Priority:  Normal       |  Milestone:
 Component:  base         |    Version:
Resolution:               |   Keywords:
      Port:               |
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Comment (by cjones051073):

 See https://github.com/macports/macports-base/pull/283

 Also not a couple ports are now requesting this standard

 {{{
 Oberon ~/Projects/MacPorts/ports > git grep cxx_standard | grep 2020
 science/seqan3/Portfile:compiler.cxx_standard   2020
 sysutils/vtm/Portfile:compiler.cxx_standard   2020
 }}}

 Currently requesting c++20 will be effectively falling back to doing what
 requesting 2017 does, which definitely includes compilers that do not
 support the 2020 standard.

-- 
Ticket URL: <https://trac.macports.org/ticket/62677#comment:3>
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