Link sigchain to main executable

 Also export necessary symbols to preempt calls from
 libart.so

Bug: 15345057
Bug: 15426766

(cherry picked from commit 96e0cfa721925550b1cc39cdfd6084a878e6ffe2)

Change-Id: I0930d96edde7dc0636e8d50d7c778f099237f748
2 files changed