gn2bp: change update_results.sh to build //base:base

Removing other targets as they are all contained within //base:base.
Although //base:base does not successfully build yet, it does succeed in
building an Android.bp file seeing changes reflected in a larger group
of targets is valuable.

Test: none
Change-Id: I328bff0fb4eb17d2020f72c8afdeebfc1bcfedfd