document how to debug bpfloader failures am: e49e0c60cd

Original change: https://android-review.googlesource.com/c/platform/system/bpf/+/1896605

Change-Id: Ib243829d791547f7680ca0c78111616e6c6377c6
tree: 0bd3156e404771ac9fd3c91ecc04f64d97f03d41
  1. bpfloader/
  2. libbpf_android/
  3. progs/
  4. Android.bp
  5. NOTICE
  6. OWNERS
  7. OWNERS_bpf
  8. PREUPLOAD.cfg