Octave 6.0.90 release candidate Octave.app build

[Andrew Janke]

Hi folks,

I've put together an Octave.app build of the Octave 6.0.90 release
candidate, if anyone would like a convenient way of testing this out on Mac.

https://github.com/octave-app/octave-app/releases/tag/v6.0.90-rc1

Requires macOS 10.14 or later (because I'm getting build errors on 10.13).

This build is done against the newish Qt 5.15 LTS release.

I have high hopes that this release might fix the "freezing GUI" issue
that's been plaguing us on Mac: the 6.0.90 GUI has been running fine for
me on macOS 10.14 so far.

Cheers,
Andrew