Cache Python packages to reduce the bandwidth usage of PyPI.

.github/workflows/cpp-python-build.yml

@@ -89,6 +89,15 @@ jobs:
           sudo apt-get install cxxtest valgrind binutils-dev
       - name: Checkout JSBSim
         uses: actions/checkout@v4
+      - name: Cache Python packages & CTest cost data
+        # CTestCostData.txt is used by CTest to optimize the distribution of the
+        # tests between the CPU cores and reduce execution time.
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cache/pip
+            build/Testing/Temporary/CTestCostData.txt
+          key: ${{ runner.os }}-${{ hashFiles('tests/CMakeLists.txt', 'python/requirements.tx') }}
       - name: Set up Python 3.8
         uses: actions/setup-python@v5
         with:
@@ -118,13 +127,6 @@ jobs:
         run: |
           mkdir build && cd build
           cmake -DCPACK_GENERATOR=DEB -DINSTALL_JSBSIM_PYTHON_MODULE=ON -DCMAKE_C_FLAGS_DEBUG="-g -O2" -DCMAKE_CXX_FLAGS_DEBUG="-g -O2" -DCMAKE_BUILD_TYPE=Debug -DSYSTEM_EXPAT=${{matrix.expat}} -DBUILD_SHARED_LIBS=${{matrix.shared_libs}} -DBUILD_JULIA_PACKAGE=${{matrix.build_julia}} -DFPECTL_DISPLAY_STACK_TRACE=${{matrix.display_stack_trace}} -DCMAKE_PREFIX_PATH=$JSBSIM_PREFIX_PATH -DCMAKE_INSTALL_PREFIX=/usr ..
-      - name: Cache CTest cost data
-        # This file is used by CTest to optimize the distribution of the tests
-        # between the cores and reduce execution time.
-        uses: actions/cache@v4
-        with:
-          path: build/Testing/Temporary/CTestCostData.txt
-          key: ${{ runner.os }}-${{ hashFiles('tests/CMakeLists.txt') }}
       - name: Build JSBSim
         working-directory: build
         run: make --jobs=$(nproc)