Set up a layered build for CI similar to what EW does

.github/workflows/build-element-call.yaml

@@ -14,6 +14,11 @@ on:
         description: The build mode for vite. Must be either 'development' or 'production'
         required: false
         default: production
+      layered:
+        type: boolean
+        description: Build against the matching branch of matrix-js-sdk (if any) instead of the locked commit.
+        required: false
+        default: false
     secrets:
       SENTRY_ORG:
         required: true
@@ -43,8 +48,15 @@ jobs:
           cache: "pnpm"
           node-version-file: ".node-version"
       - name: Install dependencies
+        if: ${{ !inputs.layered }}
         # ignore-pnpmfile should never be commited. Make CI crash if it happened (`pnpmfileChecksum` is present)
         run: "pnpm install --frozen-lockfile --ignore-pnpmfile"
+      - name: Install dependencies (layered)
+        if: ${{ inputs.layered }}
+        # ignore-pnpmfile should never be commited. Make CI crash if it happened (`pnpmfileChecksum` is present)
+        run: "scripts/layered.sh --ignore-pnpmfile"
+        env:
+          PR_HEAD_REPO_OWNER: ${{ github.event.pull_request.head.repo.owner.login }}
       - name: Build Element Call
         run: pnpm run build:"$PACKAGE":"$BUILD_MODE"
         env: