macOS: update scripts for producing and signing dmg

[vlsi]

I guess the updated scripts are here: https://github.com/JetBrains/intellij-community/tree/0e39cd4e47b173df75a904c71ff3426cbd4beb37/platform/build-scripts/tools/mac/scripts

macOS 11.x Big Sur requires app notarization: https://developer.apple.com/documentation/xcode/notarizing_macos_software_before_distribution

Do you still use createDmg to produce dmgs for mbeddr?

[sergej-koscejev]

I'm not aware of anybody building Mac DMGs at the moment.

[vlsi]

Let me clarify: I tried to modernize https://github.com/Hardella/ide61131 build once again (I attempt it once a year 😂 ), and now I bumped again into missing features in mps-gradle-plugin.

I'm not much keen on forking the plugin as the third plugin with exactly the same name and different set of features would be sad.

I think I could try the above scripts from intellij-community (I guess the license there is compatible), and I have macOS machine, so I can verify how it works.
However, I wonder what is your opinion on mergability of something like #70