Use -target 8 for apksigner am: 49f89a1c2f am: 744c13d5f7 am: 10f6ee3e8b

Original change: https://googleplex-android-review.googlesource.com/c/platform/tools/apksig/+/12272775

Change-Id: I2e802de0d50b623956cf51658e9f2dc88832bde5