Building the Python package from source fails for Windows/Python 3.9

[bcoconni]

The Python package for condais built by the JSBSim feedstock on conda-forge (which I recently created). Following the PR conda-forge/jsbsim-feedstock#5 on that project , the build fails for Windows/Python 3.9.

The failure is due to an argument to the compiler not being placed between double quotes on Python 3.9:

• Windows/Python 3.8 "/DJSBSIM_VERSION=\"1.1.4 [GitHub build 262/commit 366b9d4e35eebbcc95b9eda09f1de8b15564e281]\""
• Windows/Python 3.9 /DJSBSIM_VERSION=\"1.1.4 [GitHub build 262/commit 366b9d4e35eebbcc95b9eda09f1de8b15564e281]\"

This issue can be reproduced on JSBSim by modifying .github/worflows/cpp-python-build.yml to compile the Python package from source with Python 3.9

@@ -345,10 +345,10 @@ jobs:
        os: [ubuntu-latest, macos-latest, windows-latest]
    runs-on: ${{ matrix.os }}
    steps:
-      - name: Set up Python 3.7
+      - name: Set up Python 3.9
        uses: actions/setup-python@v1
        with:
-          python-version: '3.7'
+          python-version: '3.9'
      - name: Install Python packages
        run: pip install -U cython numpy
      - name: Download binary files

This change makes the build fail for the exact same reason than on conda-forge/jsbsim-feedstock which rules out the PR from conda-forgeas being the cause of the failure.

[bcoconni]

Issue fixed by commit 151f6b9 (as shown by the successful build of our Conda package for Windows/Python 3.9)