Fix build on macos

[michaelkirk]

Building on macos fails (I think it's related to aarch64 specifically, but I've never tested on the decreasingly relevant x86 mac).

See an attempt to build on macos here:
#331 (comment)

I briefly looked into it previously - IIRC I think the immediate error is that there is no precompiled version of fontnik for aarch64, so the container falls back to building the package from source, but the container doesn't have the necessary build deps. Installing the build deps produces another error while performing the build. I gave up at this point.

Some possible solutions might entail fixing the fontnik build or replacing/removing fontnik.

[ellenhp]

I had some issues with this in the past. I think fontnik might need to be replaced or run in emulation. Valhalla has also had some issues in the past with arm64 due to signed/unsigned char issues. The fork of valhalla in the headway org has a fix for this, someone else may have upstreamed it independently though, since it's been several years.