workflows: build: Update actions/checkout to v6

Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Author: nathanchance

.github/workflows/build.yml

@@ -7,7 +7,7 @@ jobs:
   build-test:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
     - name: Install dependencies
       run: bash ci.sh deps
     - name: Build LLVM