ci: introduce CIFuzz

Per-PR fuzzing provided by OSS-Fuzz using GH workflows.

See: https://google.github.io/oss-fuzz/getting-started/continuous-integration/

.github/workflows/main.yml

@@ -0,0 +1,27 @@
+---
+# vi: ts=2 sw=2 et:
+# See: https://google.github.io/oss-fuzz/getting-started/continuous-integration/
+
+name: CIFuzz
+on: [pull_request]
+jobs:
+ Fuzzing:
+   runs-on: ubuntu-latest
+   steps:
+   - name: Build Fuzzers
+     uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
+     with:
+       oss-fuzz-project-name: 'systemd'
+       dry-run: false
+   - name: Run Fuzzers
+     uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
+     with:
+       oss-fuzz-project-name: 'systemd'
+       fuzz-seconds: 600
+       dry-run: false
+   - name: Upload Crash
+     uses: actions/upload-artifact@v1
+     if: failure()
+     with:
+       name: artifacts
+       path: ./out/artifacts