ABI Hash should contains env var used by CMake

[bansan85]

Under Linux, it's possible to pass environment variables to CMake though vcpkg. It's not possible under Windows except with VCPKG_ENV_PASSTHROUGH.

So I can build a C++/CMake project that uses vcpkg.json with the following command.

CXXFLAGS="/fsanitize=address" cmake ...... "-DCMAKE_TOOLCHAIN_FILE=D:/vcpkg/scripts/buildsystems/vcpkg.cmake"

With this line, all vcpkg's dependency will be built and cached with sanitizer feature.

If I later run:

cmake ...... "-DCMAKE_TOOLCHAIN_FILE=D:/vcpkg/scripts/buildsystems/vcpkg.cmake"

without sanitizer, the cache will be restored with sanitizer feature.

I suggest that all environment variables used by CMake must be used to compute ABI Hash

[dg0yt]

I suggest you avoid relying on these env vars (except for limited experimentation without binary caching) and remove them where you can. They affect host and target triplets at the same time.

However, using a specific triplet file (i.e. overlay triplet) to set the enviroment variables should just work. The file content is part of the ABI hash, and the desired specific value will take effect when portfiles invoke CMake in project mode.

[BillyONeal]

Unfortunately too many of those variables have absolute paths in them which would entirely break binary caching. We should probably denylist known variables like that and set them to empty.