ci: delay checking ci/skip/multi-arch-build label

When a GitHub Event is created, the labels of the PR are set to the
current values. Mergify will only set the labels, or copy the labels to
the PR once the PR is created. That means the initial GitHub Event does
not have the right labels set yet.

In order to really skip the multi-arch-build, and run single-arch-build
instead, the label needs to be checked from the PR, instead of compared
from the labels in the GitHub Event.

Signed-off-by: Niels de Vos <[email protected]>

Author: nixpanic

.github/workflows/build-multi-stage.yaml

@@ -19,16 +19,37 @@ jobs:
     name: multi-arch-build
     runs-on: ubuntu-latest
     steps:
+      - name: delay a minute to have labels added
+        run: sleep 1m
+      - name: detect single-arch-build
+        # yamllint disable-line rule:line-length
+        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd  # v8.0.0
+        id: detect-single-arch-build
+        with:
+          script: |
+            const pr = github.rest.pulls.get({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              pull_number: github.event.pull_request.number,
+            })
+
+            for (const l of pr.labels) {
+              if (l === 'ci/skip/multi-arch-build') {
+                return true
+              }
+            }
+
+            return false
+          result-encoding: bool
+
       # yamllint disable-line rule:line-length
       - uses: actions/checkout@8e8c483db84b4bee98b60c0593521ed34d9990e8  # v6.0.1
       - name: multi-arch-build
-        # yamllint disable-line rule:line-length
-        if: ${{ ! contains(github.event.pull_request.labels.*.name, 'ci/skip/multi-arch-build') }}
+        if: !steps.detect-single-arch-build.outputs.is-single-arch-build
         # podman cannot pull images with both tag and digest
         # https://github.com/containers/buildah/issues/1407
         # use docker to build images
         run: CONTAINER_CMD=docker ./scripts/build-multi-arch-image.sh
       - name: single-arch-build
-        # yamllint disable-line rule:line-length
-        if: ${{ contains(github.event.pull_request.labels.*.name, 'ci/skip/multi-arch-build') }}
+        if: steps.detect-single-arch-build.outputs.is-single-arch-build
         run: make containerized-build