Figure out how to portably link our C dependencies statically

[emberian]

Right now our build has substantial problems building on macOS because our dependencies assume the linker is GNU ld. On macOS the linker is not GNU ld. We need to be using -force_load on macOS, so that dlsym will see all the symbols we expect at runtime. -force_load takes a full path to a static library. There's also no equivalent to -Bstatic to make the linker consider static libraries before dynamic ones when trying to satisfy an -lfoo request.

[emberian]

We can use Configurator (or, really, anything) to generate a flags.sexp that we then use with (link_flags (:include flags.sexp))

[emberian]

Done in #1443 and #1433

[emberian]

we finished this!