On windows the environment is generally cleaned:

https://learn.microsoft.com/en-us/vcpkg/users/config-environment#vcpkg_keep_env_vars

A list of passed through env variables by default can be found here:

https://github.com/microsoft/vcpkg-tool/blob/43e0cb2407ed7b85aa74a41e59e8be6b5780edb6/src/vcpkg/base/system.process.cpp#L550