We have some team members that do local development on their mac. When running docker packaging from mac, the build step will succeed but an incompatible pex_binary gets loaded into the built container -- which fails at runtime. This can be very confusing for beginners. This is basically the issue described here. I think the long term solution of allowing to build from a local docker context described here is a good one. However, in the meantime, it would be great if we could output an error at build time so people on the team (most of whom are using pants for the first time) can catch errors early on. Is there some simple way for me to hack this check into our pants build process? Maybe some sort of conditional check in the build file?

Yeah this seems like an unfortunate gotcha that we should cover. Same thing with building AWS Lambdas, actually.