[chore] run codeowner check on PRs (open-telemetry#36285)

Co-authored-by: Evan Bradley <[email protected]>

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

@@ -229,11 +229,6 @@ jobs:
         run: |
           make gendistributions
           git diff -s --exit-code || (echo 'Generated code is out of date, please run "make gendistributions" and commit the changes in this PR.' && exit 1)
-      - name: Gen CODEOWNERS
-        if: (github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/v')) && github.repository == 'open-telemetry/opentelemetry-collector-contrib'
-        run: |
-          GITHUB_TOKEN=${{ secrets.READ_ORG_AND_USER_TOKEN }} make gengithub
-          git diff -s --exit-code || (echo 'Generated code is out of date, please apply this diff and commit the changes in this PR.' && git diff && exit 1)
       - name: CodeGen
         run: |
           make -j2 generate

.github/workflows/check-codeowners.yaml

@@ -0,0 +1,60 @@
+name: codeowners
+on:
+  push:
+    branches: [main]
+    tags:
+      - "v[0-9]+.[0-9]+.[0-9]+*"
+  pull_request_target:
+    types:
+      - opened
+      - synchronize
+      - edited
+      - reopened
+env:
+  # Make sure to exit early if cache segment download times out after 2 minutes.
+  # We limit cache download as a whole to 5 minutes.
+  SEGMENT_DOWNLOAD_TIMEOUT_MINS: 2
+
+# Do not cancel this workflow on main. See https://github.com/open-telemetry/opentelemetry-collector-contrib/pull/16616
+concurrency:
+  group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  setup-environment:
+    timeout-minutes: 30
+    runs-on: ubuntu-latest
+    if: ${{ github.actor != 'dependabot[bot]' }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-go@v5
+        with:
+          go-version: "1.22.8"
+          cache: false
+      - name: Cache Go
+        id: go-cache
+        timeout-minutes: 5
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/go/bin
+            ~/go/pkg/mod
+            ./.tools
+          key: go-cache-${{ runner.os }}-${{ hashFiles('**/go.sum') }}
+  check-codeowners:
+    runs-on: ubuntu-latest
+    needs: [setup-environment]
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{github.event.pull_request.head.ref}}
+          repository: ${{github.event.pull_request.head.repo.full_name}}
+          path: pr
+      - name: Gen CODEOWNERS
+        if: github.repository == 'open-telemetry/opentelemetry-collector-contrib'
+        run: |
+          make githubgen-install
+          cd pr
+          GITHUB_TOKEN=${{ secrets.READ_ORG_AND_USER_TOKEN }} githubgen
+          git diff -s --exit-code || (echo 'Generated code is out of date, please apply this diff and commit the changes in this PR.' && git diff && exit 1)