The downside of this approach to serialization is that when we add file
X.scm to the list of objects to build serially, we force a full rebuild
whenever X.scm is modified.  At present, eval.scm is the only file that
forces a full rebuild.  Your patch would add psyntax-pp.scm to that
list.

I don't feel strongly about it, and maybe your patch is still a net
benefit, but I very much wish we had a better way to optimize the early
bootstrap without adding these bogus dependencies.

> To which branch should this be applied, stable-2.2 or master?

If we decide to adopt this approach, it should probably be committed to
stable-2.2, but first I'd like to give other people an opportunity to
share their thoughts on this.

Thoughts?