Detect workflow file changes to trigger LKL build

Previously, the nightly LKL build only checked the hash of the LKL
commit, so the build process will only be triggered when the upstream
LKL has new commit. However, if the build-lkl.yml is updated, the LKL
should be rebuilt.

This checks not only the LKL commit hash but the hash of build-lkl.yml
to ensure the build process is triggered when build-lkl.yml is updated.

Change-Id: I8db1dc2c1fea03bd8dc85d767e6298739d4a9f35

Author: rota1001

.github/workflows/build-lkl.yml

@@ -36,8 +36,12 @@ jobs:
       contents: read
     outputs:
       lkl_commit: ${{ steps.head.outputs.commit }}
+      yml_hash: ${{ steps.compare.outputs.yml_hash }}
       needs_build: ${{ steps.compare.outputs.needs_build }}
     steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
       - name: Get upstream LKL HEAD
         id: head
         run: |
@@ -54,25 +58,37 @@ jobs:
         env:
           GH_TOKEN: ${{ github.token }}
         run: |
+          CURRENT_YML=$(sha256sum .github/workflows/build-lkl.yml | awk '{print $1}')
+          echo "yml_hash=${CURRENT_YML}" >> "$GITHUB_OUTPUT"
+
           if [ "${{ inputs.force }}" = "true" ]; then
             echo "needs_build=true" >> "$GITHUB_OUTPUT"
             echo "Forced rebuild requested."
             exit 0
           fi
 
           # Fetch BUILD_INFO from existing nightly release.
-          LAST_COMMIT=$(gh release view "${{ env.NIGHTLY_TAG }}" \
+          LAST_RELEASE=$(gh release view "${{ env.NIGHTLY_TAG }}" \
             --repo "${{ env.KBOX_REPO }}" \
-            --json body --jq '.body' 2>/dev/null \
+            --json body --jq '.body' 2>/dev/null) || LAST_RELEASE=""
+
+          LAST_COMMIT=$(echo "$LAST_RELEASE" \
             | grep -oP 'commit=\K[0-9a-f]+' | head -1) || LAST_COMMIT=""
 
-          CURRENT="${{ steps.head.outputs.commit }}"
-          if [ "$LAST_COMMIT" = "$CURRENT" ]; then
-            echo "needs_build=false" >> "$GITHUB_OUTPUT"
-            echo "Upstream unchanged (${CURRENT}). Skipping build."
-          else
+          LAST_YML=$(echo "$LAST_RELEASE" \
+            | grep -oP 'yml_hash=\K[0-9a-f]+' | head -1) || LAST_YML=""
+
+          CURRENT_COMMIT="${{ steps.head.outputs.commit }}"
+
+          if [ "$LAST_COMMIT" != "$CURRENT_COMMIT" ]; then
+            echo "needs_build=true" >> "$GITHUB_OUTPUT"
+            echo "New upstream commit: ${CURRENT_COMMIT} (was: ${LAST_COMMIT:-none})"
+          elif [ "$LAST_YML" != "$CURRENT_YML" ]; then
             echo "needs_build=true" >> "$GITHUB_OUTPUT"
-            echo "New upstream commit: ${CURRENT} (was: ${LAST_COMMIT:-none})"
+            echo "build-lkl.yml was changed"
+          else
+            echo "needs_build=false" >> "$GITHUB_OUTPUT"
+            echo "Upstream unchanged (${CURRENT_COMMIT}) and the build script unchanged. Skipping build."
           fi
 
   # ---- Build x86_64, aarch64 and riscv64 in parallel ----
@@ -144,12 +160,14 @@ jobs:
           GH_TOKEN: ${{ github.token }}
         run: |
           LKL_COMMIT="${{ needs.check-upstream.outputs.lkl_commit }}"
+          YML_HASH="${{ needs.check-upstream.outputs.yml_hash }}"
           BUILD_DATE=$(date -u +%Y-%m-%dT%H:%M:%SZ)
 
           cat > /tmp/release-notes.md <<EOF
           Nightly prebuilt liblkl.a for kbox.
 
           commit=${LKL_COMMIT}
+          yml_hash=${YML_HASH}
           date=${BUILD_DATE}
           upstream=https://github.com/${{ env.LKL_UPSTREAM }}/commit/${LKL_COMMIT}