change index used on getsitepackages

* on windows, the first element in the result list is the venv directory, the second is the actual site-packages directory
* on ubuntu/macos, the list only contains one element, so index -1 works for both

.github/workflows/build_executable.yml

@@ -44,11 +44,8 @@ jobs:
         run: uv pip install pyinstaller
 
       - name: Find site package directory
-        run: echo "sitepackage_dir=$(python -c "import site; print(site.getsitepackages()[0])")" >> $GITHUB_ENV
-
-      - run: python -c "import site; print(site.getsitepackages())"
-      - run: ls $sitepackage_dir
-      - run: ls $sitepackage_dir/Lib/site-packages
+        run: echo "sitepackage_dir=$(python -c "import site; print(site.getsitepackages()[-1])")" >> $GITHUB_ENV
+        # On ubuntu/macos, getsitepackages returns a list with only one element, on windows a list with two elements is returned where the second is correct.
 
       - name: Build executable
         run: uv run pyinstaller --onefile --add-data "$sitepackage_dir/license_expression/data/scancode-licensedb-index.json:./license_expression/data" --add-data "$sitepackage_dir/spdx_tools/spdx/parser/tagvalue/*:./spdx_tools/spdx/parser/tagvalue" src/opossum_lib/cli.py