The problem is not that MIT Scheme uses libxcb and it is missing.  The problem is threefold:

1. The bootstrap build tries to link against X11 needlessly.
2. The build fails late during make, not early during configure, when linking against libX11 fails.
3. Using -lX11 brought in a static libX11.a, which is probably not the right thing -- although I don't know in this case.

On an ELF system and perhaps others, if you link against a static libX11.a, when libX11 normally depends on libxcb, then the normal recursive shared library dependency mechanism of ELF doesn't kick in because the libraries are static.  Instead, if you want to link with -lX11, you must also pass -lxcb and similar for every library libX11 depends on itself.

... after a build time of over an hour.

ideally, building a command line compiler should not involve any X11 libraries at all - so i assume it's only used for some plugin or code library.

the configure script should check if those optional dependencies exist, and if not exclude the code using them from the build process.

if they're not optional, an error message at configure time is appropriate.