Map zlib to zlib-ng

[donny-dont]

Remove the zlib port implementation and instead create an empty zlib port that depends on zlib-ng.

[donny-dont]

Implementation idea taken from microsoft/vcpkg#30743

[dg0yt]

Don't forget to remove vcpkg-cmake and vcpkg-cmake-config.

[donny-dont]

Thanks for catching that and the general technique!

[dg0yt]

The show-stopper might be the lack of activating ZLIB_COMPAT. AFAICS it is not (and cannot be) mapped to a feature, and so it would need to be injected by triplet file customization.

[donny-dont]

That's disappointing. The whole point of zlib-ng is to have a drop in replacement.

You have an example on how one would inject it?

[donny-dont]

Looks like https://learn.microsoft.com/en-us/vcpkg/users/triplets#vcpkg_cmake_configure_options

[dg0yt]

"Drop-in replacement" is the same as "alternative", and vcpkg is unable to allow alternatives.

Basically, all (overlay) triplet files need

if(PORT STREQUAL "zlib-ng")
    set(VCPKG_CMAKE_CONFIGURE_OPTIONS "-DZLIB_COMPAT=ON")
endif()

(There are other efforts, but I don't think anything is ready now.)

[donny-dont]

Alrighty so it seems like the port itself needs a change to make this work

if(ZLIB_COMPAT)
    set(_cmake_dir "ZLIB")
else()
    set(_port_suffix "zlib-ng")
endif()
vcpkg_cmake_config_fixup(CONFIG_PATH lib/cmake/${_cmake_dir})

Can wait until microsoft/vcpkg#43122 lands before proposing the changes.