Windows: Linking errors with libmccs_stubs.a

[bryphe]

We're using this project on esy as part of our solver infrastructure: https://github.com/andreypopp/esy-solve-cudf , and it works great! We're now working to enable this solver on Windows, however, and we hit a linking error when building that esy-solve-cudf project:

** Cannot resolve symbols for C:/Users/bryph/.esy/3_/i/opam__slash__mccs-1.1+8-e4af6af7/lib\mccs\libmccs_stubs.a(lexagregate_combiner.o/
notuptodate_criteria.o/
removed_criteria.o/
):
 _ZTVN10__cxxabiv117__class_type_infoE
 _ZTVN10__cxxabiv121__vmi_class_type_infoE

It looks like these are RTTI symbols.

[dra27]

You need a patched flexlink to support C++ linking - the patch is in the AppVeyor script (sorry, awkward
to do the link from my phone)

[bryphe]

Thanks @dra27 ! Got it - I'll test it out and see if that fixes my issue. 👍

[bryphe]

Confirmed it's fixed when I brought in your PR ocaml/flexdll#48 for flexdll - no other compiler flags needed. Thanks again @dra27 !