[ci] Script for building M1 wheels (#19925)

This PR includes a script for building wheels for Macs with M1 processors. It roughly follows the pattern of the other scripts with a few differences.

Manually installs nvm
Uses miniforge conda to install python/pip instead of python foundation .pkgs
Doesn't pin numpy (we probably shouldn't be pinning it in the other scripts either...)
Commit detection falls back to git instead of erroring
All of these changes were made so that the script works on a laptop, which comes with a subset of the dependencies that the x86 buildkite image comes with.

python/build-wheel-macos-arm64.sh

@@ -0,0 +1,92 @@
+#!/bin/bash
+
+# Cause the script to exit if a single command fails.
+set -e
+
+# Show explicitly which commands are currently running.
+set -x
+
+DOWNLOAD_DIR=python_downloads
+
+NODE_VERSION="14"
+PY_VERSIONS=("3.8.2"
+             "3.9.1")
+PY_MMS=("3.8"
+        "3.9")
+
+
+if [[ -n "${SKIP_DEP_RES}" ]]; then
+  ./ci/travis/install-bazel.sh
+
+  curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.39.0/install.sh | bash
+  curl -o- https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge3-MacOSX-arm64.sh | bash
+  source ~/.bash_profile
+  conda init bash
+  source ~/.bash_profile
+
+  # Use the latest version of Node.js in order to build the dashboard.
+  source "$HOME"/.nvm/nvm.sh
+  nvm install $NODE_VERSION
+  nvm use $NODE_VERSION
+fi
+
+# Build the dashboard so its static assets can be included in the wheel.
+pushd python/ray/dashboard/client
+  npm ci
+  npm run build
+popd
+
+mkdir -p .whl
+
+for ((i=0; i<${#PY_VERSIONS[@]}; ++i)); do
+  PY_MM=${PY_MMS[i]}
+  CONDA_ENV_NAME="p$PY_MM"
+
+  # The -f flag is passed twice to also run git clean in the arrow subdirectory.
+  # The -d flag removes directories. The -x flag ignores the .gitignore file,
+  # and the -e flag ensures that we don't remove the .whl directory.
+  git clean -f -f -x -d -e .whl -e $DOWNLOAD_DIR -e python/ray/dashboard/client -e dashboard/client
+
+
+  # Install python using conda. This should be easier to produce consistent results in buildkite and locally.
+  source ~/.bash_profile
+  conda create -y -n "$CONDA_ENV_NAME"
+  conda activate "$CONDA_ENV_NAME"
+  conda remove -y python || true
+  conda install -y python="$PY_MM"
+
+  # NOTE: We expect conda to set the PATH properly.
+  PIP_CMD=pip
+  PYTHON_EXE=python
+
+  $PIP_CMD install --upgrade pip
+
+  if [ -z "${TRAVIS_COMMIT}" ]; then
+    TRAVIS_COMMIT=${BUILDKITE_COMMIT}
+  fi
+
+  pushd python
+    # Setuptools on CentOS is too old to install arrow 0.9.0, therefore we upgrade.
+    $PIP_CMD install --upgrade setuptools
+    $PIP_CMD install -q cython==0.29.15
+    # Install wheel to avoid the error "invalid command 'bdist_wheel'".
+    $PIP_CMD install -q wheel
+    # Set the commit SHA in __init__.py.
+    if [ -n "$TRAVIS_COMMIT" ]; then
+      echo "TRAVIS_COMMIT variable detected. ray.__commit__ will be set to $TRAVIS_COMMIT"
+    else
+      echo "TRAVIS_COMMIT variable is not set, getting the current commit from git."
+      TRAVIS_COMMIT=$(git rev-parse HEAD)
+    fi
+
+    sed -i .bak "s/{{RAY_COMMIT_SHA}}/$TRAVIS_COMMIT/g" ray/__init__.py && rm ray/__init__.py.bak
+
+    # Add the correct Python to the path and build the wheel. This is only
+    # needed so that the installation finds the cython executable.
+    # build ray wheel
+    $PYTHON_EXE setup.py bdist_wheel
+    # build ray-cpp wheel
+    RAY_INSTALL_CPP=1 $PYTHON_EXE setup.py bdist_wheel
+    mv dist/*.whl ../.whl/
+  popd
+done