app: build fake auxv

Some Android systems cannot read from /proc/self/auxv. Work around
this by creating a minimal fake auxv for the Go runtime.

Fixes #9229

Change-Id: Id2d743f43d91be23006aac708a5b5b5cd60a6dca
Reviewed-on: https://go-review.googlesource.com/1284
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>