Add support for linux/arm64 wheels.

Update pyproject.toml to build for aarch64 on Linux, and update
release_linux.sh to download the corresponding bazelisk binary.
Also download setuptools and wheel on host and install them in before-build
with --no-build-isolation to avoid transient PyPI timeout issues in container.

PiperOrigin-RevId: 933297845

Author: dmitriplotnikov

release/kokoro/release_linux.sh

@@ -203,7 +203,12 @@ rm -rf cel_expr_python/*_test.py
 
 echo "Downloading bazelisk on host..."
 curl -LO https://github.com/bazelbuild/bazelisk/releases/download/v1.19.0/bazelisk-linux-amd64
-chmod +x bazelisk-linux-amd64
+curl -LO https://github.com/bazelbuild/bazelisk/releases/download/v1.19.0/bazelisk-linux-arm64
+chmod +x bazelisk-linux-amd64 bazelisk-linux-arm64
+
+echo "Downloading build dependencies on host..."
+mkdir -p build_deps
+pip download --only-binary=:all: --dest build_deps "setuptools>=40.8.0" "wheel"
 
 # Check if pyproject.toml exists before running sed
 if [ -f pyproject.toml ]; then

release/pyproject.toml

@@ -44,14 +44,18 @@ test-command = "python {project}/cel_basic_test.py"
 build-verbosity = 1
 
 [tool.cibuildwheel.linux]
+build-frontend = { name = "pip", args = ["--no-build-isolation"] }
+before-build = "pip install --no-index --find-links={project}/build_deps setuptools wheel"
+archs = ["x86_64", "aarch64"]
 manylinux-x86_64-image = "manylinux_2_28"
+manylinux-aarch64-image = "manylinux_2_28"
 container-engine = "docker; disable_host_mount: True"
 # Google's internal Kokoro/RBE network uses a secure MITM proxy that resigns HTTPS
 # traffic with an internal Google CA. Since the public manylinux container does not
 # trust this CA, git fetches for external dependencies (like @cel-cpp) will fail
 # with SSL certificate errors. We disable http.sslVerify inside the container to
 # bypass this and allow Bazel to fetch SCM dependencies through the proxy.
-before-all = "git config --global http.sslVerify false && echo 'Installing bazelisk' && cp {project}/bazelisk-linux-amd64 /usr/local/bin/bazel"
+before-all = "git config --global http.sslVerify false && echo 'Installing bazelisk' && if [ $(uname -m) = 'aarch64' ]; then cp {project}/bazelisk-linux-arm64 /usr/local/bin/bazel; else cp {project}/bazelisk-linux-amd64 /usr/local/bin/bazel; fi"
 
 [tool.cibuildwheel.macos]
 before-all = "echo 'Installing bazelisk'; brew install bazelisk"