Generate vendor_boot-chd_debug.img while building CHD am: fa55c6d3a6

Original change: https://android-review.googlesource.com/c/platform/tools/treble/+/2969433

Change-Id: I59e697dfbac9a6a01bf864ef7725c76e00da5fdd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>