CI: enable GHA macos builds

[chipitsine]

No description provided.

[chipitsine]

@barracuda156 , please review

[barracuda156]

@chipitsine I am afraid I cannot be useful with CI setups.

@catap Could you take a quick look at this?

[barracuda156]

@chipitsine On our buildbots everything is good: https://ports.macports.org/port/softether5/details
(Build failure on 10.7 and 10.10 look superficial and unrelated to softether itself; all other versions are good, including PowerPC build – the latter verified locally, no buildbot for it atm.)

[chipitsine]

@barracuda156 , what is "macports" ?

if that is kind of package manager, can you add a link to it to our doc ?
how regular ar those builds ? can we add badge ?

[barracuda156]

@chipitsine Macports is one of the two arguably most widely used package managers on macOS. (It might also work on Linux and FreeBSD, but that is seldom tested.)

Buildbots will rebuild a port every time it is updated. A user may choose to install a pre-built package then or build from source.

Yes, I can add a reference in install-for-macOS section, if it is there.

[chipitsine]

great, we'll appreciate that