CI: add support for merge queue

.github/workflows/extra-builds.yml

@@ -1,23 +1,20 @@
 name: Test extra build flows
 
 on:
-  # always test main
-  push:
-    branches:
-      - main
-  merge_group:
-  # test PRs
   pull_request:
-  # allow triggering tests, ignores skip check
+  merge_group:
+  #push:
+  #  branches: [ main ]
   workflow_dispatch:
 
 jobs:
   pre_job:
     runs-on: ubuntu-latest
     outputs:
-      should_skip: ${{ steps.skip_check.outputs.should_skip }}
+      should_skip: ${{ steps.set_output.outputs.should_skip }}
     steps:
       - id: skip_check
+        if: ${{ github.event_name != 'merge_group' }}
         uses: fkirc/skip-duplicate-actions@v5
         with:
           # don't run on documentation changes
@@ -26,11 +23,19 @@ jobs:
           # but never cancel main
           cancel_others: ${{ github.ref != 'refs/heads/main' }}
 
+      - id: set_output
+        run: |
+          if [ "${{ github.event_name }}" = "merge_group" ]; then
+            echo "should_skip=false" >> $GITHUB_OUTPUT
+          else
+            echo "should_skip=${{ steps.skip_check.outputs.should_skip }}" >> $GITHUB_OUTPUT
+          fi
+
   vs-prep:
     name: Prepare Visual Studio build
     runs-on: ubuntu-latest
     needs: [pre_job]
-    if: needs.pre_job.outputs.should_skip != 'true'
+    if: (github.event_name == 'merge_group' || github.event_name == 'workflow_dispatch') && needs.pre_job.outputs.should_skip != 'true'
     steps:
       - uses: actions/checkout@v4
         with:
@@ -48,7 +53,7 @@ jobs:
     name: Visual Studio build
     runs-on: windows-latest
     needs: [vs-prep, pre_job]
-    if: needs.pre_job.outputs.should_skip != 'true'
+    if: (github.event_name == 'merge_group' || github.event_name == 'workflow_dispatch') && needs.pre_job.outputs.should_skip != 'true'
     steps:
       - uses: actions/download-artifact@v4
         with:
@@ -65,7 +70,7 @@ jobs:
   wasi-build:
     name: WASI build
     needs: pre_job
-    if: needs.pre_job.outputs.should_skip != 'true'
+    if: (github.event_name == 'merge_group' || github.event_name == 'workflow_dispatch') && needs.pre_job.outputs.should_skip != 'true'
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4
@@ -111,7 +116,7 @@ jobs:
   nix-build:
     name: "Build nix flake"
     needs: pre_job
-    if: needs.pre_job.outputs.should_skip != 'true'
+    if: (github.event_name == 'merge_group' || github.event_name == 'workflow_dispatch') && needs.pre_job.outputs.should_skip != 'true'
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
@@ -126,3 +131,13 @@ jobs:
         with:
           install_url: https://releases.nixos.org/nix/nix-2.30.0/install
       - run: nix build .?submodules=1 -L
+
+  extra-builds-result:
+    runs-on: ubuntu-latest
+    needs:
+      - vs-build
+      - wasi-build
+      - nix-build
+    if: always() && !contains(join(needs.*.result, ','), 'failure') && !contains(join(needs.*.result, ','), 'cancelled')
+    steps:
+      - run: echo "All good"