feat(android): add Rust cross-compilation setup for Android environment

[ririv]

Like platform windows

cibuildwheel/cibuildwheel/platforms/windows.py

Lines 206 to 232 in c53e541

	def setup_rust_cross_compile(
	tmp: Path, # noqa: ARG001
	python_configuration: PythonConfiguration,
	python_libs_base: Path, # noqa: ARG001
	env: MutableMapping[str, str],
	) -> None:
	# Assume that MSVC will be used, because we already know that we are
	# cross-compiling. MinGW users can set CARGO_BUILD_TARGET themselves
	# and we will respect the existing value.
	cargo_target = {
	"64": "x86_64-pc-windows-msvc",
	"32": "i686-pc-windows-msvc",
	"ARM64": "aarch64-pc-windows-msvc",
	}.get(python_configuration.arch)
	# CARGO_BUILD_TARGET is the variable used by Cargo and setuptools_rust
	if env.get("CARGO_BUILD_TARGET"):
	if env["CARGO_BUILD_TARGET"] != cargo_target:
	log.notice("Not overriding CARGO_BUILD_TARGET as it has already been set")
	# No message if it was set to what we were planning to set it to
	elif cargo_target:
	log.notice(f"Setting CARGO_BUILD_TARGET={cargo_target} for cross-compilation")
	env["CARGO_BUILD_TARGET"] = cargo_target
	else:
	log.warning(
	f"Unable to configure Rust cross-compilation for architecture {python_configuration.arch}"
	)

Add Rust cross-compilation setup for Android environment, it can fix the cross-compilation problem for the rust project built with setuptools-rust

[ririv]

For Rust projects built with Maturin, it currently does not work. Maturin has some cross-compilation issues on Android that still need to be fixed.

For details, please see PyO3/maturin#2810

[joerick]

This looks nice and neat! Is there an example of it working in a real project that you've been testing it with?

[ririv]

I want to test， but I did not know how to run this without the github action，if you know how to do, you can tell me，and I will test it.

This commit is a modification I made based on the actual missing environment configuration built on Android using cbuildwheel.

Of course, I manually configured it externally in a non-isolated environment, and after the configuration, I built the wheel correctly and it can run on Android

[joerick]

You can test a project using something like this in a github workflow-

      - name: Build wheels
        uses: ririv/cibuildwheel@main

[ririv]

Thanks, I have tested it, and made some new commits. Now, it works.

• The CARGO_TARGET_<triple>_LINKER must be set. Otherwise, it will use the host's linker cc, which will result in an error.
• The PYO3_CROSS_LIB_DIR must be set to link against libpython3.x.so explicitly.
  See: https://peps.python.org/pep-0738/#linkage and https://pyo3.rs/v0.27.1/building-and-distribution.html#cross-compiling

The PYO3_CROSS_LIB_DIR environment variable should be set here rather than requiring users to specify it manually, for the following reasons:

• PYO3 has become the de facto standard for Python extension modules built with Rust. Both setuptools-rust and maturin are tools developed by the PYO3 team specifically to serve PYO3.
• The value set for PYO3_CROSS_LIB_DIR requires the directory path of target_python. This path is already configured within cbuildwheel's android.py but cannot be directly accessed externally. External configuration would necessitate manually constructing the path.
• PYO3's documentation for Android cross-compilation is insufficiently detailed. If users attempt to set this variable manually, they are likely to become confused and unsure how to proceed.

[ririv]

https://github.com/ririv/android-wheels/blob/main/.github/workflows/cbuildweel-repair-test.yml
This is the workflow file. It performed some conversions.
For the maturin project, it was converted to a setuptools-rust project. This is because maturin has some bugs in Android cross-compilation. I've submitted a PR to fix it, but the maturin maintainer hasn't responded yet.

Here are some logs:

• pydantic-core | maturin convert to setuptools-rust
  https://github.com/ririv/android-wheels/actions/runs/19223626338/job/54946144941
• tiktoken | based on setuptools-rust
  https://github.com/ririv/android-wheels/actions/runs/19223649349/job/54946212372