chore: use integration tests support files when calculating cache key for fixtures (#554)

Co-authored-by: Mateusz Bocian <mrstork@users.noreply.github.com>

Author: pieh

.github/workflows/run-tests.yml

@@ -146,10 +146,10 @@ jobs:
           echo "Resolved Next.js version for 'next@${{ matrix.version }}' is '$RESOLVED_VERSION'"
       - name: Compute Fixtures Cache Key
         id: fixture-cache-key
-        # Fixtures only need to be rebuilt if anything in the tests/fixtures directory changes,
-        # so we're using a hash of the files in that directory as the cache key.
+        # Fixtures only need to be rebuilt if either fixture or support files change,
+        # so we're using a hash of the fixtures and support files as the cache key.
         run:
-          echo "key=$(git ls-files -s tests/fixtures/ tests/prepare.mjs | git hash-object --stdin)"
+          echo "key=$(git ls-files -s tests/fixtures/ tests/utils/ tests/prepare.mjs | git hash-object --stdin)"
           >> "$GITHUB_OUTPUT"
         shell: bash
       - name: Cache Fixtures