In 0d2b00c7e9, I introduced a setting for
the virtual file defines class cache to avoid ooms coming from zinc
stamping the project jar files. I introduced that cache at the compile
level though rather than global level and crashes were still occurring
in the sbt build. It was very easy to induce a crash on my computer by
running compile a few times, reload and then compile again. After making
the cache global, the crashes went away.