Access environment variables in config-settings

[sarlinpe]

Description

It would be handy to set config-settings based on some environment variables, for example when both the build and the before-all process need the same arguments, such as here using vcpkg:

[tool.cibuildwheel.macos]
before-all = "cd dependencies && cmake -DCMAKE_TOOLCHAIN_FILE=${CMAKE_TOOLCHAIN_FILE} && ..."

[tool.cibuildwheel.macos.environment]
VCPKG_INSTALLATION_ROOT = "/Users/runner/work/vcpkg"
CMAKE_TOOLCHAIN_FILE = "${VCPKG_INSTALLATION_ROOT}/scripts/buildsystems/vcpkg.cmake"
CMAKE_OSX_ARCHITECTURES = "${CIBW_ARCHS_MACOS}"

[tool.cibuildwheel.macos.config-settings]
"cmake.define.CMAKE_TOOLCHAIN_FILE" = "${CMAKE_TOOLCHAIN_FILE}"
"cmake.define.VCPKG_TARGET_TRIPLET" = "${VCPKG_TARGET_TRIPLET}"
"cmake.define.CMAKE_OSX_ARCHITECTURES" = "${CIBW_ARCHS_MACOS}"

Currently this doesn't work, though the doc does not make it clear. I think that this would require setting shell=True:

cibuildwheel/cibuildwheel/util.py

Line 127 in f11f1b2

result = subprocess.run(args_, check=True, shell=IS_WIN, env=env, cwd=cwd, **kwargs)

But I'm unsure about potential side effects.

Build log

No response

CI config

No response