Changed EncodeFEC to compute in incremental steps allowing OTA to be am: bd16b01e41

Original change: https://android-review.googlesource.com/c/platform/system/update_engine/+/2246875

Change-Id: I5e74c523f0638b4806d2e2ad0b678da6ce9c0947
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>