[Ur] Statically linking Ur/Web runtime

[Benjamin Barenblat]

Currently, Ur/Web builds as a compiler and a set of shared libraries,
and compiled Ur/Web executables dynamically link those libraries. This
seems error-prone: The Ur/Web libraries are intended only for use by
Ur/Web applications, and their APIs and ABIs are somewhat unstable
(cf. https://github.com/urweb/urweb/issues/40). I think we should be
statically linking the Ur/Web runtime into Ur/Web applications. Doing so
would improve portability, prevent Ur/Web updates from breaking existing
binaries, and improve startup time for the CGI backend. It would also
open the door to cross-object inlining and other forms of link-time
optimization, which could improve performance substantially. What do you
think?