After moving the darwin/arm builder to new hardware several new flaky
error messages appeared. This provided enough information to Google
to make it clear that iOS build systems have been flaky for many
years, and that is unlikely to change any time soon.

However, all of the pain of lldb and using a breakpoint early in
program initialization gives us an advantage: all install and
initialization flakiness appears to happen before the Go program ever
gets going. So if we see an error or we timeout before we reach our
breakpoint (before any test code has executed), we can assume it is
the fault of the builder and restart without risking hiding a flaky
Go test.

This code has successfully processed the last 8 builds. I am hopeful.

Change-Id: Ide24aaae4fa7bdab9d8f4432bb85d8f2256c7606
Reviewed-on: https://go-review.googlesource.com/8241Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>