[asan] Override default sigaltstack setting on Android.
[asan] Override default sigaltstack setting on Android.

Android libc always sets altstack on non-main threads, but it is too small for
our unwinder. With use_sigaltstack=1, override this setting with a larger one.


git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@201557 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt,llvm-mirror/compiler-rt