Revert "serial run"

This reverts commit 6504151.

Author: JalinWang

.github/workflows/05-windows-build.yml

@@ -84,7 +84,7 @@ jobs:
         run: |
           cd "$env:GITHUB_WORKSPACE"
           $env:CMAKE_GENERATOR = "Ninja"
-          $env:CMAKE_BUILD_PARALLEL_LEVEL = "1"
+          $env:CMAKE_BUILD_PARALLEL_LEVEL = "$env:NPROC"
           python -m pip install -v . `
             --no-build-isolation `
             --config-settings='cmake.define.BUILD_TOOLS=ON'