Install cibuildwheel from requirements file

So Renovate can update them all at the same time

Author: hugovk

.ci/requirements-cibw.txt

@@ -0,0 +1 @@
+cibuildwheel==2.16.2

.github/workflows/wheels.yml

@@ -52,10 +52,14 @@ jobs:
         with:
           submodules: true
 
-      - name: Build wheels
-        uses: pypa/[email protected]
+      - uses: actions/setup-python@v4
         with:
-          output-dir: wheelhouse
+          python-version: "3.x"
+
+      - name: Build wheels
+        run: |
+          python3 -m pip install -r .ci/requirements-cibw.txt
+          python3 -m cibuildwheel --output-dir wheelhouse
         env:
           CIBW_ARCHS: ${{ matrix.archs }}
           CIBW_BUILD: ${{ matrix.build }}

.travis.yml

@@ -35,7 +35,7 @@ jobs:
         - CIBW_BUILD="*musllinux*"
 
 install:
-    - python3 -m pip install cibuildwheel==2.16.2
+    - python3 -m pip install -r .ci/requirements-cibw.txt
 
 script:
     - python3 -m cibuildwheel --output-dir wheelhouse