When the DBM database cannot be read by the current version of Ruby's
DBM library (due to corruption or another incompatibility) it segfaults
or freezes which takes down the entire Homebrew Ruby process.
This isn't desirable so instead perform a shell out with the Homebrew
Ruby to see if it can read the DBM database before we try to use the
information. If this hangs or crashes: silently delete the database and
recreate it.
