I don't have 7zip installed from the alpine package repository because I specifically want rar support, and rather than rebuilding the 7zip package I opted to just compile 7zip support into YACReader.

I don't think the problem compiling the devel version is with 7zip though. For example, by default it wasn't finding the T libraries. Alpine has all the needed packages and is FHS compliant so it shouldn't be an issue. At least as far as compiling it works fine with the release version but not the devel version, so something must have changed between those versions for it not to generate the Makefile properly.

I'm happy to provide as much info as I can to help troubleshoot if that is desired, but I don't think it's anything strange with my system or missing packages. It's a pretty fresh install, no weird deviations or anything.

I'm going to try and rebuilding the Alpine 7zip package with rar support as selmf suggested, and will look at using libarchive as well.