[ChibiScheme] add builder

[stevengj]

Add a builder for Chibi-Scheme, which is a minimal self-contained embeddable Scheme interpreter.

[giordano]

Progress! At Linux is working now, the other failures sounds like they're related to the fact the build system believes we're always targeting Linux?

[stevengj]

Yes.

Some of the problems should be solved by just not building image files, which are an optional optimization—it's not clear if it will be practical to cross-compile them in the current setup. Have to figure out how to omit this from the build.

Another problem is that the chibi-ffi script needs to be tweaked for cross-compiling; I'm currently looking into this.

[imciner2]

Closing due to inactivity. Please submit a new PR on top of the current master branch if you still want to include this recipe.