Skip cache delete job for forked PRs

.github/workflows/ci.yml

@@ -226,6 +226,8 @@ jobs:
     needs:
     - test_22_unit
     - test_22_extra_diagnose
+    if: github.actor != 'dependabot[bot]' && github.event.pull_request.head.repo.fork
+      == false
     runs-on: ubuntu-latest
     steps:
     - name: Checkout project
@@ -342,6 +344,8 @@ jobs:
     needs:
     - test_20_unit
     - test_20_extra_diagnose
+    if: github.actor != 'dependabot[bot]' && github.event.pull_request.head.repo.fork
+      == false
     runs-on: ubuntu-latest
     steps:
     - name: Checkout project
@@ -458,6 +462,8 @@ jobs:
     needs:
     - test_18_unit
     - test_18_extra_diagnose
+    if: github.actor != 'dependabot[bot]' && github.event.pull_request.head.repo.fork
+      == false
     runs-on: ubuntu-latest
     steps:
     - name: Checkout project

Rakefile

@@ -197,6 +197,10 @@ namespace :build_matrix do
             unit_test_job_key,
             diagnose_job_key
           ],
+          # Skip this job for dependabot and forked PRs as they do not
+          # have write permissions to the repository to delete caches
+          "if" => "github.actor != 'dependabot[bot]' && " \
+            "github.event.pull_request.head.repo.fork == false",
           "runs-on" => "ubuntu-latest",
           "steps" => [
             {