Build and cache numpy=1.16 aarch64 wheels

Author: janaknat

.github/workflows/cibuildwheel.yml

@@ -36,10 +36,27 @@ jobs:
         with:
           python-version: '3.7'
 
+      - uses: actions/cache@v2
+        id: numpy-aarch64-cache
+        with:
+          path: numpy-aarch64-cache/
+          key: numpy-aarch64-cache
+
       - name: Install cibuildwheel
         run: |
           python -m pip install cibuildwheel==1.9.0
 
+      - name: Build numpy 1.16 for aarch64
+        if: matrix.cibw_archs == 'aarch64' && steps.numpy-aarch64-cache.outputs.cache-hit != 'true'
+        run: |
+          wget https://files.pythonhosted.org/packages/04/b6/d7faa70a3e3eac39f943cc6a6a64ce378259677de516bd899dd9eb8f9b32/numpy-1.16.0.zip
+          unzip numpy-1.16.0.zip
+          cd numpy-1.16.0
+          python -m cibuildwheel --output-dir ../numpy-aarch64-cache
+        env:
+          CIBW_BUILD: "cp36-* cp37-* cp38-*"
+          CIBW_ARCHS: aarch64
+
       - name: Copy setup.cfg to configure wheel
         run: |
           cp setup.cfg.template setup.cfg
@@ -62,7 +79,7 @@ jobs:
           CIBW_BUILD: "cp37-* cp38-*"
           CIBW_MANYLINUX_X86_64_IMAGE: manylinux1
           CIBW_MANYLINUX_I686_IMAGE: manylinux1
-          CIBW_BEFORE_BUILD: pip install certifi oldest-supported-numpy
+          CIBW_BEFORE_BUILD: pip install certifi; pip install --find-links=numpy-aarch64-cache/ numpy==1.16
           MPL_DISABLE_FH4: "yes"
           CIBW_ARCHS: ${{ matrix.cibw_archs }}
 
@@ -73,7 +90,7 @@ jobs:
           CIBW_BUILD: "cp36-*"
           CIBW_MANYLINUX_X86_64_IMAGE: manylinux1
           CIBW_MANYLINUX_I686_IMAGE: manylinux1
-          CIBW_BEFORE_BUILD: pip install certifi oldest-supported-numpy
+          CIBW_BEFORE_BUILD: pip install certifi; pip install --find-links=numpy-aarch64-cache/ numpy==1.16
           MPL_DISABLE_FH4: "yes"
           CIBW_ARCHS: ${{ matrix.cibw_archs }}
         if: >
@@ -85,7 +102,7 @@ jobs:
           python -m cibuildwheel --output-dir dist
         env:
           CIBW_BUILD: "pp3?-*"
-          CIBW_BEFORE_BUILD: pip install certifi oldest-supported-numpy
+          CIBW_BEFORE_BUILD: pip install certifi numpy==1.16
           CIBW_ARCHS: ${{ matrix.cibw_archs }}
         if: >
           runner.os != 'Windows' && (