github: Skip clang-analyze when reference generation fails.

By assuming that OVS maintainers never push changes that breaks
compilation in GHA (which seems to be the case so far), it seems natural
to assume that generating the reference for clang analyzer should always
work.

If generating this reference fails, it is likely due to a change external
to OVS code, and not due to the series being tested (though this series
gets flagged with an error in patchwork).

Such a situation is often hit in the dpdk-latest branch when some DPDK
API change breaks OVS compilation and no OVS fix is merged yet.

Split the clang analyzer check in two jobs:
- a clang-analyze-cache job, responsible for computing a cache key of the
  reference code and compiling a reference build,
- a clang-analyze job, which depends on the former job, responsible for
  compiling the current patch and comparing the result against the
  reference,

The cache generation won't be reported as a failure at the OVS build step
(using continue-on-error:).
If such a failure happens, the cache-analyzer job is skipped.

Fixes: d662eee ("ci: Add clang-analyze to GitHub actions.")
Signed-off-by: David Marchand <[email protected]>

.github/workflows/build-and-test.yml

@@ -332,7 +332,7 @@ jobs:
         name: logs-linux-${{ join(matrix.*, '-') }}
         path: logs.tgz
 
-  build-clang-analyze:
+  build-clang-analyze-cache:
     needs: build-dpdk
     env:
       dependencies: |
@@ -341,7 +341,10 @@ jobs:
       CC:   clang
       DPDK: dpdk
       CLANG_ANALYZE: true
-    name: clang-analyze
+    name: clang-analyze-cache
+    outputs:
+      key: ${{ steps.cache_key.outputs.key }}
+      outcome: ${{ steps.build_base.outcome }}
     runs-on: ubuntu-24.04
     timeout-minutes: 30
 
@@ -412,35 +415,86 @@ jobs:
         key:  ${{ steps.cache_key.outputs.key }}
 
     - name: set up python
+      if: steps.clang_cache.outputs.cache-hit != 'true'
       uses: actions/setup-python@v5
       with:
         python-version: ${{ env.python_default }}
 
     - name: get cached dpdk-dir
+      if: steps.clang_cache.outputs.cache-hit != 'true'
       uses: actions/cache/restore@v4
       with:
         path: dpdk-dir
         key:  ${{ needs.build-dpdk.outputs.dpdk_key }}
 
     - name: update APT cache
+      if: steps.clang_cache.outputs.cache-hit != 'true'
       run:  sudo apt update || true
 
     - name: install common dependencies
+      if: steps.clang_cache.outputs.cache-hit != 'true'
       run:  sudo apt install -y ${{ env.dependencies }}
 
     - name: prepare
+      if: steps.clang_cache.outputs.cache-hit != 'true'
       run:  ./.ci/linux-prepare.sh
 
     - name: build base reference
+      id: build_base
       if: steps.clang_cache.outputs.cache-hit != 'true'
+      continue-on-error: true
       run:  ./.ci/linux-build.sh
 
-    - name: save cache
-      uses: actions/cache/save@v4
-      if: steps.clang_cache.outputs.cache-hit != 'true'
+  build-clang-analyze:
+    needs: [build-dpdk, build-clang-analyze-cache]
+    if: >
+        needs.build-clang-analyze-cache.outputs.outcome == 'success' ||
+        needs.build-clang-analyze-cache.outputs.outcome == 'skipped'
+    env:
+      dependencies: |
+        automake bc clang-tools libnuma-dev libunbound-dev libunwind-dev \
+        libssl-dev libtool libxdp-dev llvm-dev
+      CC:   clang
+      DPDK: dpdk
+      CLANG_ANALYZE: true
+    name: clang-analyze
+    runs-on: ubuntu-24.04
+    timeout-minutes: 30
+
+    steps:
+    - name: checkout
+      uses: actions/checkout@v4
+
+    - name: update PATH
+      run: |
+        echo "$HOME/bin"        >> $GITHUB_PATH
+        echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+    - name: check for analyzer result cache
+      uses: actions/cache/restore@v4
       with:
         path: base-clang-analyzer-results
-        key:  ${{ steps.cache_key.outputs.key }}
+        key:  ${{ needs.build-clang-analyze-cache.outputs.key }}
+
+    - name: set up python
+      uses: actions/setup-python@v5
+      with:
+        python-version: ${{ env.python_default }}
+
+    - name: get cached dpdk-dir
+      uses: actions/cache/restore@v4
+      with:
+        path: dpdk-dir
+        key:  ${{ needs.build-dpdk.outputs.dpdk_key }}
+
+    - name: update APT cache
+      run:  sudo apt update || true
+
+    - name: install common dependencies
+      run:  sudo apt install -y ${{ env.dependencies }}
+
+    - name: prepare
+      run:  ./.ci/linux-prepare.sh
 
     - name: build
       run:  ./.ci/linux-build.sh