message: Don't set opt_level to best
  LICM is still broken
diff: @@ -242,7 +242,8 @@ fn build_isa(sess: &Session) -> Box<dyn isa::TargetIsa + 'static> {
  "false"
  }).unwrap();
  - flags_builder.set("opt_level", "best").unwrap();
  + // FIXME(CraneStation/cranelift#732) fix LICM in presence of jump tables
  + //flags_builder.set("opt_level", "best").unwrap();
  // FIXME enable again when https://github.com/CraneStation/cranelift/issues/664 is fixed
  /*
  