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

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



Change-Id: Iaa334e5e134a66d26b318b07a8ab9e9fed3d503b
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>