Use glyphsLib minimal builds

[khaledhosny]

This tells glyphsLib to create enough UFO for building binary fonts and discard any unneeded data.

This requires glyphsLib 6.0.0 or later.

[khaledhosny]

Looks like pypy3 does not like the new glyphsLib parser.

[anthrotype]

uh-oh yes.. fonttools/openstep-plist#12

[anthrotype]

I had not realised that with glyphsLib 6 and the concomitant switch to openstep-plist parser, we would lose pypy support. That's a pity, but for the time being there's no quick fix and we may have to temporarily drop support for pypy until we figure out how to make it happy. I suggest we open an issue here and/or on glyphsLib to track this, linking to fonttools/openstep-plist#12, and here we temporarily comment out the pypy3 tests in the CI config file (with a TODO and a link to the issue)

[khaledhosny]

we temporarily comment out the pypy3 tests in the CI config file (with a TODO and a link to the issue)

Done

[anthrotype]

I think we can tag a major version bump v3.0.0b1 instead of v2.5.0b1 -- given we dropped support for python 3.6 and pypy3, we add support for Glyphs 3, we will soon. add support for iondrive (#802)

[khaledhosny]

Sounds good.

[anthrotype]

@khaledhosny https://pypi.org/project/fontmake/3.0.0b1/

[khaledhosny]

Thanks!