Use pyopencl wheel from silx.org under Windows

.gitlab-ci.yml

@@ -53,7 +53,8 @@ debian10:
   variables:
     WITH_GL_TEST: "False"
   script:
-    - pip install pybind11  # Needed to build pyopencl under Windows
+    # Install pyopencl first to use a wheel from silx.org under Windows
+    - pip install --find-links http://www.silx.org/pub/wheelhouse/ --trusted-host www.silx.org --only-binary pyopencl pyopencl
     - pip install --pre --find-links artifacts/ --only-binary silx silx[full]
     - python -c "import silx.test, sys; sys.exit(silx.test.run_tests());"