Merge "Make 'mkbootfs' print a usage message for insufficent args." am:...

Merge "Make 'mkbootfs' print a usage message for insufficent args." am: 4cc0cb2b am: e591c7d1 am: abe12d93 am: cb1f13db

Original change: https://android-review.googlesource.com/c/platform/system/core/+/2152273



Change-Id: I169c10506433e3441519a8d23cf4c96ce3ecf1c6
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>