workflows: Use unique build ids (#823)

Build ids on the fileserver simply used the GITHUB_RUN_ID, but it is not
guaranteed to be unique, and other repositories and workflows share the
same tree. Change build ids to be prefixed with the GITHUB_REPOSITORY
name, and suffixed with the GITHUB_RUN_ATTEMPT (in case the run has been
given back).

This is still safe from the perspective of directory names and URLs as
GitHub prevents org and repo names to start with a dash, and use only
alphanumeric chars plus single dashes.

Author: ndechesne

.github/workflows/build-yocto.yml

@@ -8,9 +8,10 @@ on:
         value: ${{ jobs.create-output.outputs.url }}
 
 env:
+  BUILD_ID: ${{ github.repository }}-${{ github.run_id }}-${{ github.run_attempt }}
   CACHE_DIR: /srv/gh-runners/quic-yocto
   KAS_REPO_REF_DIR: /srv/gh-runners/quic-yocto/kas-mirrors
-  BASE_ARTIFACT_URL: "https://quic-yocto-fileserver-1029608027416.us-central1.run.app/${{ github.run_id }}"
+  BASE_ARTIFACT_URL: https://quic-yocto-fileserver-1029608027416.us-central1.run.app
 
 jobs:
   kas-mirror:
@@ -113,7 +114,7 @@ jobs:
 
       - name: Publish image
         run: |
-          build_dir=${CACHE_DIR}/builds/${GITHUB_RUN_ID}
+          build_dir=${CACHE_DIR}/builds/${BUILD_ID}
           mkdir -p $build_dir
           img_dir=$build_dir/${{ matrix.machine }}
           [ -d $img_dir ] && rm -rf $img_dir
@@ -122,7 +123,7 @@ jobs:
           mv $deploy_dir $img_dir
 
           # Instruct our file server to make these files available for download
-          url="${BASE_ARTIFACT_URL}/${{ matrix.machine }}/"
+          url="${BASE_ARTIFACT_URL}/${BUILD_ID}/${{ matrix.machine }}/"
 
           retries=8
           okay=0
@@ -157,9 +158,10 @@ jobs:
       - name: "Print output"
         id: print-output
         run: |
-          echo "Downloads URL: ${BASE_ARTIFACT_URL}"
-          echo "url=\"${BASE_ARTIFACT_URL}\"" >> $GITHUB_OUTPUT
-          echo "${BASE_ARTIFACT_URL}" > build_url
+          build_url="${BASE_ARTIFACT_URL}/${BUILD_ID}"
+          echo "Downloads URL: ${build_url}"
+          echo "url=\"${build_url}\"" >> $GITHUB_OUTPUT
+          echo "${build_url}" > build_url
       - name: Upload build URL
         uses: actions/upload-artifact@v4
         with: