RFR: 8314488: Compile the JDK as C++17 [v2]

[Kim Barrett]

On Fri, 15 Dec 2023 15:52:07 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

> gcc: https://gcc.gnu.org/gcc-9/changes.html
> "The C++17 implementation is no longer experimental."

Bumping to gcc10 rather than gcc9 would have the benefit that we could get a work-alike for C++20
`std::is_constant_evaluated` even though we're not otherwise using C++20.  Sufficiently recent versions
of all of our supported compilers provide `__builtin_is_constant_evaluated`.  That first shows up in gcc10.
We're already requiring versions of clang and msvc that provide it.  There are a bunch of potential improvements
we could make by having such a work-alike.

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PR Comment: https://git.openjdk.org/jdk/pull/14988#issuecomment-1895511862