mysql8: update to 8.0.27

[chrstphrchvz]

Requires C++17
Closes: https://trac.macports.org/ticket/60894

Use MacPorts' libc++ on macOS 10.11 and earlier for std::shared_timed_mutex
See: https://trac.macports.org/ticket/60853

Description

https://dev.mysql.com/doc/relnotes/mysql/8.0/en/news-8-0-27.html

Type(s)

• bugfix

Tested on

macOS 10.15.7
Xcode 12.4 command line tools

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL?
• checked your Portfile with port lint?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?

[macportsbot]

Notifying maintainers:
@herbygillot for port mysql8.

[chrstphrchvz]

Other things to eventually check include whether https://trac.macports.org/ticket/63456 still applies, and whether the port will now build on macOS 10.12-10.13.

[chrstphrchvz]

Rebased to incorporate 9a562be (fix for https://trac.macports.org/ticket/63641)

[chrstphrchvz]

Added legacysupport.use_mp_libcxx yes to attempt to fix https://trac.macports.org/ticket/60853

[chrstphrchvz]

Will have to pare back this PR since someone else already updated the port: ca0a578

[reneeotten]

closed by ca0a578