Default clang in Ubuntu 16.04 is broken

[zrax]

Describe the bug
Attempting to use the default clang (version 3.8) from the ubuntu-16.04 image runs into incompatibilities with the libstdc++ provided on the same image.

Virtual environments affected

• macOS 10.14
• Ubuntu 16.04 LTS
• Ubuntu 18.04 LTS
• Windows Server 2016 R2
• Windows Server 2019

Expected behavior
The provided clang++ from Ubuntu should be able to compile code that would otherwise work on an Ubuntu 16.04 machine.

Actual behavior
It appears the provided libstdc++ is from GCC 7, whereas the default in Ubuntu is from GCC 5. When using libstdc++ 7, many standard C++ headers run into errors such as:

In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0/../../../../include/c++/7.4.0/memory:62:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0/../../../../include/c++/7.4.0/bits/stl_algobase.h:64:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0/../../../../include/c++/7.4.0/bits/stl_pair.h:59:
In file included from /usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0/../../../../include/c++/7.4.0/bits/move.h:54:
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.4.0/../../../../include/c++/7.4.0/type_traits:2661:5: error: 'inline' can only appear on functions
    _GLIBCXX17_INLINE constexpr bool is_swappable_v =
    ^

An example can be seen here:
https://github.com/zrax/string_theory/runs/285221827

(Note also that the Travis CI build using the same OS and compiler works successfully)

[github-actions]

This issue has not had any activity for 45 days and will be closed in 45 days if there continues to be no activity.

[maxim-lobanov]

Hello!
In scope of #104, we have updated clang on Ubuntu images, could you please double check if the issue is resolved?

[zrax]

It appears to remain unresolved: https://github.com/zrax/string_theory/runs/471074583

Is there some version of clang other than the one(s) provided by apt that we should be using?

[nikita-bykov]

We made changes that should solve the issue. Ubuntu 16.04 image will be rolled out next week.

[maxim-lobanov]

Changes were deployed.
Please let me know if something doesn't work yet