Fix clang-14 run in CI

[mborland]

The updated GHA runners broke Clang-14 in C++20 mode. G++12 in C++20 mode is covered in our drone runs which are fine..

[jzmaddock]

Just out of curiosity, what was the breakage, it seems a shame we can't run clang in C++20.

[mborland]

Just out of curiosity, what was the breakage, it seems a shame we can't run clang in C++20.

There are two to watch for now. This will hit any Clang < 16 in 2b mode:

/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/bits/stl_iterator.h:2618:35: error: missing 'typename' prior to dependent type name 'iterator_traits<_It>::iterator_category'
      { using iterator_category = iterator_traits<_It>::iterator_category; };
                                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

And this will happen in C++20 mode:

/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/chrono:2320:48: error: call to consteval function 'std::chrono::hh_mm_ss::_S_fractional_width' is not a constant expression
        static constexpr unsigned fractional_width = {_S_fractional_width()};
                                                      ^
/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/chrono:2320:48: note: undefined function '_S_fractional_width' cannot be used in a constant expression
/usr/bin/../lib/gcc/x86_64-linux-gnu/13/../../../../include/c++/13/chrono:2275:2: note: declared here
        _S_fractional_width()
        ^
1 error generated.

The GHA 22.04 image updated from GCC12 to 13 as the default version a few days ago.

[ckormanyos]

The GHA 22.04 image updated from GCC12 to 13 as the default version a few days ago.

This seemingly harmless change actually broke parts of iterator_traits and parts of chrono. I spent all weekend working around in unrelated other opesn-source projects in order to keep those compilers. But you need to have super-simple uses of iterators and chrono-functions. I don't think Boost will have such simplistic cases...

Tough break on this one.