Use python executable & multiline PS args

Replace usage of the Windows py launcher with an explicit python invocation and format the PowerShell call to package-for-dart.ps1 across multiple lines.

- workflow: print the python executable (python -c) instead of calling py -3 --version, and invoke the packaging script with PowerShell line continuations for readability.
- script: switch compile step in windows/package-for-dart.ps1 from py -3 -m compileall to python -m compileall to avoid relying on the py launcher.

These changes make the CI and packaging scripts use the active python interpreter directly and improve command readability in the workflow.

Author: FeodorFitsner

.github/workflows/build-python.yml

@@ -112,11 +112,13 @@ jobs:
         shell: pwsh
         run: |
           python --version
-          py -3 --version
+          python -c "import sys; print(sys.executable)"
       - name: Build CPython from sources and package for Dart
         shell: pwsh
         run: |
-          .\windows\package-for-dart.ps1 -PythonVersion "${{ env.PYTHON_VERSION }}" -PythonVersionShort "${{ env.PYTHON_VERSION_SHORT }}"
+          .\windows\package-for-dart.ps1 `
+            -PythonVersion "${{ env.PYTHON_VERSION }}" `
+            -PythonVersionShort "${{ env.PYTHON_VERSION_SHORT }}"
       - uses: actions/upload-artifact@v4
         with:
           name: python-windows

windows/package-for-dart.ps1

@@ -110,7 +110,7 @@ foreach ($pattern in $excludePatterns) {
 }
 
 # Match existing packaging behavior: bytecode-only stdlib.
-py -3 -m compileall -b "$packageRoot\Lib"
+python -m compileall -b "$packageRoot\Lib"
 Get-ChildItem -Path "$packageRoot\Lib" -Recurse -File -Include *.py,*.typed | Remove-Item -Force
 Get-ChildItem -Path "$packageRoot\Lib" -Recurse -Directory -Filter __pycache__ | Remove-Item -Recurse -Force