Add linux aarch64 wheel build support

.github/workflows/wheel.yaml

@@ -4,13 +4,18 @@ on: [push, pull_request]
 
 jobs:
   build_wheels:
-    name: Build wheel on ${{ matrix.os }}
+    name: Build wheel on ${{matrix.arch}} for ${{ matrix.os }}
     runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, windows-latest, macos-latest]
+        arch: [auto]
+        include:
+          - os: ubuntu-latest
+            arch: aarch64
     env:
+      CIBW_ARCHS_LINUX: ${{matrix.arch}}
       CIBW_TEST_COMMAND: pytest --pyargs numcodecs
       CIBW_TEST_REQUIRES: pytest
       CIBW_SKIP: "*27* pp* *35*"
@@ -27,11 +32,23 @@ jobs:
         with:
           python-version: '3.9'
 
+      - uses: docker/setup-qemu-action@v1
+        if: ${{ matrix.arch == 'aarch64' }}
+        name: Set up QEMU
+
       - name: Install cibuildwheel
         run: |
           python -m pip install cibuildwheel==1.8.0 wheel
 
+      - name: Build wheel for aarch64
+        if: ${{ matrix.arch == 'aarch64' }}
+        env:
+          CIBW_ENVIRONMENT: 'DISABLE_NUMCODECS_AVX2=1 DISABLE_NUMCODECS_SSE2=1'
+        run: |
+          python -m cibuildwheel --output-dir wheelhouse
+
       - name: Build wheel
+        if: ${{ matrix.arch != 'aarch64' }}
         run: |
           python -m cibuildwheel --output-dir wheelhouse
       - uses: actions/upload-artifact@v1

setup.py

@@ -2,6 +2,7 @@
 import os
 from setuptools import setup, Extension
 import cpuinfo
+import platform
 import sys
 from distutils.command.build_ext import build_ext
 from distutils.errors import CCompilerError, DistutilsExecError, \
@@ -28,6 +29,8 @@
 if have_cflags:
     # respect compiler options set by user
     pass
+elif platform.machine() == 'aarch64':
+    pass
 elif os.name == 'posix':
     if disable_sse2:
         base_compile_args.append('-mno-sse2')