Avoid forcing VCPKG and allow using external dependencies

[barracuda156]

Please do not force everyone to rely on VCPKG. The build should be customizable.

The following commit brought this undesirable change: 5997aff

Using external dependencies should be supported, that is how most downstream software distributions work. We do not want VCPKG to choose some random stuff to build for us in MacPorts, for example. Otherwise this kind of tickets arise.

[teo-tsirpanis]

@barracuda156 you can disable automatic downloading of vcpkg by setting the TILEDB_DISABLE_AUTO_VCPKG environment variable to any value.

[teo-tsirpanis]

@MehdiChinoune sorry for the frustration. The packaging of lz4 has a known issue where the official and vcpkg distributions have different casing of the package names. I have made work towards unifying their behavior and will continue to do so by engaging with both lz4 and vcpkg. In the meantime you can apply a patch we have been using for Conda, that will make CMake use the standard find_library mechanism to get lz4.

I must also say that the name TILEDB_VCPKG has been a bit misleading. In the past, we were using CMake ExternalProjects to download and build our dependencies, which has been a very hard to maintain solution for various reasons. Setting -DTILEDB_VCPKG=ON disables this legacy mechanism and makes our build system exclusively use the standard CMake find_*** commands to find our dependencies. These dependencies can be provided by vcpkg which gets downloaded by default for convenience, but we are not forcing downstreams to use vcpkg. Auto-downloading it can be disabled as explained in my previous comment, and then the user can use standard CMake facilities like CMAKE_PREFIX_PATH to guide the build system to the dependencies.

Let me know if you have further questions.

[teo-tsirpanis]

Opened macports/macports-ports#24239 to migrate the tiledb port to not need to patch disabling TILEDB_VCPKG.

[teo-tsirpanis]

The MacPorts PR has been merged, I believe we can close this issue. Let us know if you encounter another problem.

[barracuda156]

@teo-tsirpanis Thank you very much.

P. S. By the way, if you or anyone will be interested to help us maintain TileDB port, welcome to be a co-maintainer.