Hello! In the qemu source tarball, roms/skiboot/ can't be built due to a trivial error: the directory lacks expected-to-be-there .version file, which can be built using roms/skiboot/make_version.sh script (which actually just runs git --describe). However it is impossible to create from the tarball since there's no .git/ directory in there.
Please include roms/skiboot/.version file in the distribution tarball. Thanks, /mjt