Fix linux_job_v2 after pytorch/test-infra#6104 (#459)

Author: amdfaa

.github/workflows/build_ffmpeg.yaml

@@ -29,6 +29,9 @@ jobs:
       matrix:
         ffmpeg-version: ["4.4.4", "5.1.4", "6.1.1", "7.0.1"]
     uses: pytorch/test-infra/.github/workflows/linux_job_v2.yml@main
+    permissions:
+      id-token: write
+      contents: read
     with:
       job-name: Build
       upload-artifact: ffmpeg-lgpl