Bump actions/checkout from 5 to 6

Bumps [actions/checkout](https://github.com/actions/checkout) from 5 to 6.
- [Release notes](https://github.com/actions/checkout/releases)
- [Changelog](https://github.com/actions/checkout/blob/main/CHANGELOG.md)
- [Commits](https://github.com/actions/checkout/compare/v5...v6)

---
updated-dependencies:
- dependency-name: actions/checkout
  dependency-version: '6'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/build-libs.yml

@@ -18,7 +18,7 @@ jobs:
       MACOSX_DEPLOYMENT_TARGET: "10.9"
     steps:
       - name: checkout portaudio
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: PortAudio/portaudio
           ref: v19.7.0
@@ -61,7 +61,7 @@ jobs:
       LDFLAGS: "/Brepro"
     steps:
       - name: checkout portaudio
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
         with:
           repository: PortAudio/portaudio
           ref: v19.7.0
@@ -95,7 +95,7 @@ jobs:
     needs: [macos, windows]
     steps:
       - name: Clone Git repository
-        uses: actions/checkout@v5
+        uses: actions/checkout@v6
       - name: Retrieve dylib
         uses: actions/download-artifact@v6
         with: