Add prebuilt/gdb/{darwin,linux}-x86 to manifest.

Bug: http://b/21920612
Change-Id: Id1a2927a300cac5dd0bafcb7e53c2b8895f2fc06
1 file changed
tree: 80d00af0d331023cb8bd46aadd6d875f46231e5c
  1. default.xml