WIP: github: Run libcxx windows tests on push

Author: mstorsjo

.github/workflows/libcxx-build-and-test.yaml

@@ -14,6 +14,7 @@
 #
 name: Build and Test libc++
 on:
+  push:
   pull_request:
     paths:
       - 'libcxx/**'
@@ -29,10 +30,6 @@ on:
 permissions:
   contents: read # Default everything to read-only
 
-concurrency:
-  group: ${{ github.workflow }}-${{ github.event.pull_request.number }}
-  cancel-in-progress: true
-
 jobs:
   stage1:
     if: github.repository_owner == 'llvm'
@@ -237,7 +234,6 @@ jobs:
 
   windows:
     runs-on: windows-2022
-    needs: [ stage2 ]
     strategy:
       fail-fast: false
       matrix: