ci: run clang-tidy

With the unity builds there doesn't seem to be an oom problem anymore. An
option is still added to the ci job, so that the number of threads can easily
be reduced in the future in case there are oom problems again.

.github/workflows/clang-tidy.yml

@@ -12,6 +12,11 @@ on:
         description: Artifact name of build dir
         required: true
         type: string
+      threads:
+        description: Parallel execution count
+        required: false
+        type: number
+        default: 0
 
 jobs:
   clang-tidy:
@@ -33,8 +38,5 @@ jobs:
       - name: Untar artifact
         run: tar -xzf build-dir.tar
       - name: Run Clang-Tidy
-        # TODO(romangg): For now we skip the actual clang-tidy operation on CI because
-        # the process consumes too much resources and the runner terminates.
-        if: false
-        run: tooling/analysis/clang-tidy.py -p build
+        run: tooling/analysis/clang-tidy.py -p build -j ${{ inputs.threads }}
         shell: bash