Stop using -fvisibility=hidden.

It breaks backtraces, and backtraces are useful. (The debugger uses
the ELF debug info, so it doesn't care, but backtracing just uses the
symbols.)

(cherry-pick of da2fb9754a9ccfa954c1b554982f06e7cf7d680a.)

Bug: 6447213
Change-Id: I957df0e935b61bcf5fefc0e506ecdaa862bc7d07
3 files changed