Update conf-freeglut for the mingw-w64 ports

[jmid]

This is modeled after the initial example PR #26072 from @dra27 (for libssl)
and a more recent one (#27553) for libevent.

[jmid]

Mumble... 🤔
It seems the MinGW package doesn't include a .pc file for pkgconf to pick up: https://www.cygwin.com/packages/x86_64/mingw64-x86_64-freeglut/mingw64-x86_64-freeglut-2.8.1-1
whereas on MSys it does include a .pc file: https://packages.msys2.org/packages/mingw-w64-x86_64-freeglut

Furthermore, I realize that Linux and FreeBSD query pkg-config glut whereas MSys registers it under the freeglut name.
https://cgit.freebsd.org/ports/tree/graphics/freeglut/pkg-plist

[shonfeder]

IIUC, this is still being worked on, so I've marked it accordingly. Please LMK if I'm misinterpreting!

[jmid]

Digging some more into this, I can see a .pc file was added upstream for the freeglut package in the 3.0.0(-rc1) release: https://github.com/freeglut/freeglut/commits/master/freeglut.pc.in

This also explains why

• it is absent on MinGW - where the freeglut package is orphaned and stuck at version 2.8.1 https://www.cygwin.com/packages/summary/mingw64-x86_64-freeglut.html while
• it is present on MSys - at version 3.6.0 https://packages.msys2.org/packages/mingw-w64-x86_64-freeglut

The MinGW failure is therefore to be expected - and unlikely to change status unless someone steps up and adopts the Cygwin package.

[jmid]

Based on the above, I've gone with

• removing the pkgconf check on MinGW - as there is no .pc file to query, yet the package can still be installed
• adjusting the check to pkg-config freeglut on MSys - which seems to be the right binary name from https://packages.msys2.org/packages/mingw-w64-x86_64-pkg-config

I've not adjusted the logic to remove the conf-pkg-config dependency on Win32 MinGW while attempting to keep it on Win32 MSys as it seemed overkill.

Finally, seeing the previous CI run failed on macOS I've added entries based on
https://formulae.brew.sh/formula/freeglut and https://ports.macports.org/port/freeglut/details/

[shonfeder]

Fantastic. Thank you for the fixes and for adding this conf- package! 🙏