Privatize zlib + friends; build shared on windows [alt.]

[h-vetinari]

Alternative to #243.

[conda-forge-linter]

Hi! This is the friendly automated conda-forge-linting service.

I just wanted to let you know that I linted all conda-recipes in your PR (recipe) and found it was in an excellent condition.

[h-vetinari]

Github got confused with having CI for the same commit run from two PRs (one cancelled), but in any case, the new run is there.

[h-vetinari]

Sidenote: The CI is running, GH just gets confused with the same commit having been cancelled in another PR.

[h-vetinari]

@isuruf, thanks for tackling the Fork bits as well, but it looks like it's not working yet (I might try bashing on it later based on what you started with).

D:\bld\grpc-split_1666422622638\work\src\core\lib\gprpp\fork.cc(252): error C2039: 'support_enabled_': is not a member of 'grpc_core::Fork'
D:\bld\grpc-split_1666422622638\work\src/core/lib/gprpp/fork.h(38): note: see declaration of 'grpc_core::Fork'
D:\bld\grpc-split_1666422622638\work\src\core\lib\gprpp\fork.cc(252): error C2374: 'grpc_core::support_enabled_': redefinition; multiple initialization
D:\bld\grpc-split_1666422622638\work\src\core\lib\gprpp\fork.cc(166): note: see declaration of 'grpc_core::support_enabled_'