environment-overrides.cmake for Linux

[tuero]

My goal is for a port to include an environment variable (LIBTORCH_ROOT) in the ABI on linux. This contains the path to a libtorch install (through a conda virtual environment). This virtual environment variable could change (if the user is in a different virtual env), and cmake configuration errors could occur.

Suppose I have a library libA, which resides in a custom registry, and a downstream repo uses libA as a dependency through the custom registry.

In the downstream project, I can use a custom triplet which has the following: set(VCPKG_ENV_PASSTHROUGH "LIBTORCH_ROOT"). This puts the environment variable LIBTORCH_ROOT into the ABI (I confirmed this by inspecting vcpkg_abi_info.txt), and when I switch virtual environments with a different path for LIBTORCH_ROOT, it rebuild and doesn't reuse any cached artifacts.

Is there a way to set this in my port directly, which doesn't depend on downstream projects setting the VCPKG_ENV_PASSTHROUGH in the triplet? I've read that for Windows at least, I can use a environment-overrides.cmake inside the port of the custom registry, but I haven't gotten this to work on linux. I'm not sure if this feature is not supported, or if it is and I have something else configured wrong which is causing this to not work for me.