Problem: fuzzing Github action ran on pushes on forks and fails

Solution: run in on PRs only as oss-fuzz uses Docker so the repository is
hard-coded

.github/workflows/CI.yaml

@@ -89,12 +89,3 @@ jobs:
       shell: cmd      
       working-directory: build_libzmq
       run: ctest -C "%Configuration%"
-  Fuzzing:
-    runs-on: ubuntu-latest
-    steps:
-    - name: Build Fuzzers
-      id: build
-      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
-      with:
-        oss-fuzz-project-name: 'libzmq'
-        dry-run: false

.github/workflows/Fuzzers.yaml

@@ -0,0 +1,13 @@
+name: Fuzzers
+on: [pull_request]
+
+jobs:
+  Fuzzing:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Build Fuzzers
+      id: build
+      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
+      with:
+        oss-fuzz-project-name: 'libzmq'
+        dry-run: false