Add i686-linux-android for gcc toolchain detection.

* Look for i686-linux-android under <sysroot>/lib/gcc.

* This patch also slightly enhance the test suite for
  Android GCC toolchain detection.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169557 91177308-0d34-0410-b5e6-96231b3b80d8
9 files changed