Try a more flexible way of finding Boost

Author: pitrou

.github/workflows/cpp.yml

@@ -190,7 +190,11 @@ jobs:
           submodules: true
       - name: Build
         shell: bash
-        run: ci/scripts/cpp_build.sh $(pwd) $(pwd)/build
+        run: |
+          export BOOST_ROOT="$(ls -1 /c/local/boost_* | tail -n1)"
+          export BOOST_LIBRARYDIR="${BOOST_ROOT}\\lib64-msvc-14.1"
+          echo "BOOST_ROOT: ${BOOST_ROOT}"
+          ci/scripts/cpp_build.sh $(pwd) $(pwd)/build
       - name: Test
         shell: bash
         run: ci/scripts/cpp_test.sh $(pwd) $(pwd)/build