It would be great to avoid relying on the environment variables. However this is libcurl, being called by a standard CMake function from a pure CMake package. And the top searches for cmake and proxy seem to suggest that they also recommend the environment varialbe approach too. 1 2 There’s some recent traffic for making it a setting in the cmake-gui but that’s also been stated as unlikely. As far as I know there’s no standard way besides using an environment variable to use a proxy within a CMake build. It also appears to be the recommended approach to for distutils or setuptoolsin python.
When we integrate a tool that doesn’t use/respect the environment variables we should definitely make sure to pass it through appropriately but until then I don’t think we’ll want to increase the complexity and just let the environment variables pass through, and that can likely be specific to that buildsystem’s integration implementation.