Pass environment variables from the before-build stage

[gnikit]

I was wondering is there an easy way to propagate settings between the before-build step and the actual build?
To cross-compile Fortran for macos-arm64 we are forced to run a script that downloads the gfortran cross-compiler, e.g.

[[tool.cibuildwheel.overrides]]
select = "*-macosx_arm64"
before-build = "bash {project}/tools/wheels/cibw_before_build_macos.sh {project}"

Only problem is that variables set in the script or even written in the shell config files (.bashrc/.zshrc) are not being picked up by the actual build, where scikit-build runs.

The only working solution that I have found is to explicitly override the environmental variables in the pyproject.toml

# Override the default environment variables with the cross-compiled ones
[tool.cibuildwheel.overrides.environment]
CC = "clang"
CXX = "clang++"
FC = "/opt/gfortran-darwin-arm64-cross/bin/arm64-apple-darwin20.0.0-gfortran"
LDFLAGS = "-L/opt/gfortran-darwin-arm64-cross/lib/gcc/arm64-apple-darwin20.0.0/11.3.0 -Wl,-rpath,/opt/gfortran-darwin-arm64-cross/lib/gcc/arm64-apple-darwin20.0.0/11.3.0"

Other packages like numpy or scipy have opted for native macos-arm64 builds via Cirrus CI ( currently for us a bit of a pain to setup)

Is there a better way of doing this?