to build any project you must:
 * mkdir and chown /opt/$project_name to the user that runs the build

to build "omnibus" itself you must:
 * use /opt/omnibus2/bin/omnibus to build omnibus
 * use /opt/omnibus/bin/omnibus to build omnibus2

to build "ruby-bundle" you must:
 * run omnibus build ruby-bundle
 * upload package with deb.sh (it's in pkg/)
 * promote package with deb.sh

other info:
 * you cannot run two builds at the same time