[asan] Fix unused variable warning.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@212272 91177308-0d34-0410-b5e6-96231b3b80d8
[asan] i686-linux-android support.

Large part of this change is required due to
  https://code.google.com/p/android/issues/detail?id=61799
dlsym() crashes when symbol resolution fails, which means
we have to limit the interceptor list instead of relying on
runtime detection.

There are minor differencies in system headers, too.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@212273 91177308-0d34-0410-b5e6-96231b3b80d8