Add libxbc for bootloader bootconfig support am: db746bf101 am: 2174268797

Original change: https://android-review.googlesource.com/c/platform/bootable/libbootloader/+/1646463

Change-Id: I8fa32e54070ad99d6507c790f808a63857088100
tree: 9ca17f2be17f89776417c94d9a6d570140c06957
  1. libxbc/
  2. vts/
  3. OWNERS