focus hidden-visibility flags

This makes things like dladdr and backtrace_symbols not totally useless on Linux.

Change-Id: I26666a76c5b50fbf88aaf9709c869de0a697bb02
Reviewed-on: https://skia-review.googlesource.com/10176
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Mike Klein <mtklein@chromium.org>
1 file changed