GHA: embrace the jank

.github/workflows/build-pr.yml

@@ -1,13 +1,12 @@
-name: Build PR
+name: 
 
+# read-write repo token
+# access to secrets
 on:
-  workflow_dispatch:
-    inputs:
-      pr_number:
-        description: 'Pull Request Number'
-        required: true
-        type: string
-  pull_request:
+  workflow_run:
+    workflows: ["Trigger PR Build"]
+    types:
+      - completed
 
 concurrency:
   group: pr-${{ github.event.inputs.pr_number || github.event.pull_request.number }}

.github/workflows/trigger-pr-build.yml

@@ -0,0 +1,26 @@
+name: Trigger PR Build
+
+on:
+  workflow_dispatch:
+    inputs:
+      pr_number:
+        description: 'Pull Request Number'
+        required: true
+        type: string
+  pull_request:
+
+concurrency:
+  group: pr-${{ github.event.inputs.pr_number || github.event.pull_request.number }}
+  cancel-in-progress: false
+
+permissions:
+  contents: write
+  pull-requests: write
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    if: github.event.repository.fork == false
+    steps:
+      - name: Do the thing
+        run: echo "Hello World"