vcpkg_cmake_config_fixup interaction with CMAKE_SYSROOT

[russelltg]

Hey all! I'm using vcpkg with a chainloaded toolchain that defines CMAKE_SYSROOT (for cross-compiling). This is all working really great, but I'm trying to setup binary caching for it and some absolute paths end up in various *Targets.cmake files. What I've done to workaround the issue for now is define an environment variable to my sysroot and added a overlay for the vcpkg-cmake-config port with this added:

if (DEFINED ENV{MY_SYSROOT})
    string(REPLACE "$ENV{MY_SYSROOT}" [[${CMAKE_SYSROOT}]] contents "${contents}")
endif()

which makes the builds portable. Is there a way this could be integrated into the upstream vcpkg-cmake-config? It doesn't seem like there's access to the CMAKE_SYSROOT variable from that script as it runs from the portfile, so it would need to depend on vcpkg-cmake-get-vars or something like that.

Or is this considered to be an unsupported vcpkg configuration and overlaying that is the correct solution?