CMake linux fix: add linker flags -lm -lutil and -ldl (when configured for dynamic loading)

[lubgr]

I tested the CMake build on Archlinux x86, where I discovered that linking fails due to the missing -lm -lutil -ldl flags. Not sure how this slipped through - this PR fixes it (also tested on an ARM Archlinux system).

[okuoku]

Hmm, is libutil should only required with pty functions thus it should go to add_compiled_library -- need to some way to pass dependency to it.

Currently,

add_stubs_library(lib/chibi/pty.stub)

how about adding LINK_LIBRARIES parameter. cmake_parse_argument can parse such argument.

add_stubs_library(lib/chibi/pty.stub LINK_LIBRARIES util)

Actually, .stub files includes metadata that indicates which library should be linked;

(c-link "util")

but I'm not sure how to extract this.

[lubgr]

That's a good suggestion! I think extracting the (c-link "util") reliably is non-trivial, while the LINK_LIBRARIES option is more doable. Needs some tweaks for the static build to work, as the dependencies needs to be collected for a collective linking when the clib.c gets generated and added to to libchibi-scheme, but it works.

[ashinn]

I can add a flag for chibi-ffi to output the linker deps, but you need a working build first.

[lubgr]

I can add a flag for chibi-ffi to output the linker deps, but you need a working build first.

Thanks for offering your help on this! Given that there currenlty is only one (c-link ...) form, might it also be fine to keep this in manual sync for now?

[ashinn]

Yes, it's fine to special case -lutil for now.

[okuoku]

I can add a flag for chibi-ffi to output the linker deps, but you need a working build first.

When building shared library version, CMake build will build chibi-scheme-bootstrap first to run chibi-ffi thus that should be fine.

Difficult part is there is no way to describe .stub files themselves as "configure" dependency -- when .stub changed to link against another (native) library, we have to regenerate CMake build files. Unfortunately there's no straightforward way to do this.

Anyway, now the patch looks fine.