How do I change the compiler vcpkg uses on macOS?

[J-M0]

I'm on macOS Monterey trying to get vcpkg to use g++-12 to build Boost because my system's clang doesn't have all the C++20 features I want to use. I can easily get CMake to use g++-12 for my own code with -DCMAKE_CXX_COMPILER but vcpkg doesn't seem to take this into account which causes linking errors when the build tries to link Boost.

This is the command I'm running to configure my project:

cmake -S . -B build -DCMAKE_CXX_COMPILER=g++-12 -DCMAKE_TOOLCHAIN_FILE=vcpkg/scripts/buildsystems/vcpkg.cmake

How can I get vcpkg to respect my compiler choice?