[racket-dev] building docs, compile collects

I would like on-demand compilation of the collects tree. It seems there
are two reasons why it doesn't exist right now
1. building the documentation requires the collects tree to be touched,
so its worthwhile to just compile everything in there
2. users might not have write access to the collects tree

I use docs.racket-lang.org almost exclusively (because its simpler for
me to open) so I'm not too concerned with 1. There are rare times when I
need local docs and in those cases I don't mind building all of
collects. And as a developer 2. is not much of a concern.

I imagine some configure switch would allow the compilation manager to
assume write access to the collects tree thus solving issue 2 and a new
`make' install target that only copies the binaries to bin/ would solve 1.

My motivation is to quickly test changes to core libraries (like
collects/racket) after doing a 'git pull --rebase'.

How hard would something like this be?