Ask autobuilds to build every revision that lands here

Nothing connected a commit on this branch to a build of it: the nightly
moved when a person went and started one. Every push to the development
branch now announces its exact revision to autobuilds, which decides
whether it is worth building -- it deduplicates by build_id, so a
revision it already built costs one job and no runners.

The `run_build` listeners this repository carried were the same idea
from the other direction and no sender ever existed. Keeping them while
the name means "autobuilds, build this" would leave a dispatch able to
start a full build here by accident.

Author: frangarcj

.github/workflows/build.yml

@@ -3,8 +3,6 @@ name: Build
 on:
   push:
   pull_request:
-  repository_dispatch:
-    types: [run_build]
 
 # A push to a branch with an open pull request fires both triggers; one
 # group per head commit keeps a single run of the pair alive.

.github/workflows/dispatch-build.yml

@@ -0,0 +1,25 @@
+name: Announce a revision to autobuilds
+
+# Discovery starts here: every commit that lands on the development branch
+# is a new build input, and autobuilds is told about it. It deduplicates by
+# build_id, so announcing a revision it already built costs one job.
+on:
+  push:
+    branches: [master]
+
+jobs:
+  announce:
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Ask autobuilds to build this revision
+        env:
+          GH_TOKEN: ${{ secrets.REPO_DISPATCH_TOKEN }}
+        shell: bash
+        run: |
+          if [[ -z "$GH_TOKEN" ]]; then
+            echo "::error::REPO_DISPATCH_TOKEN secret is required for cross-repo dispatch to vitasdk/autobuilds"
+            exit 1
+          fi
+          gh api repos/vitasdk/autobuilds/dispatches \
+            -f event_type=run_build \
+            -f client_payload[buildscripts_ref]="$GITHUB_SHA"