Attempt to fix DMGs

[tresf]

CircleCI's failing, the DMG name is too long. I suspect this is caused by our new versioning logic.

There's an upstream bug report from 2015, doesn't seems like it will be fixed anytime soon, so patching it with CMake for now.

LinusU/node-appdmg#48

[LmmsBot]

🤖 Hey, I'm @LmmsBot from github.com/lmms/bot and I made downloads for this pull request, click me to make them magically appear! 🎩

Windows

• Windows 32-bit: lmms-1.3.0-alpha.2%2Bgb55f7e314-mingw-win32.exe (build link)
• Windows 64-bit: lmms-1.3.0-alpha.2%2Bgb55f7e314-mingw-win64.exe (build link)

Linux

• Linux (AppImage): lmms-1.3.0-alpha.2%2Bgb55f7e3-linux-x86_64.AppImage (build link)

macOS

• macOS : lmms-1.3.0-alpha.2%2Bgb55f7e314-mac10.13.dmg (build link)

🤖

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