One thing to note here is that building gkrust has memory requirements that make it not possible anymore to build it on 32bit systems, at least in some configurations. Not sure if we are affected by it but see https://groups.google.com/forum/#!topic/mozilla.dev.platform/XB1d2tNju3A for some discussion in case we are.
I think we are done here. For Linux the bundles are still reproducible. If there will be Rust related issues on macOS and Windows, let's open separate tickets.
Trac: Status: new to closed Resolution: N/Ato fixed