[asan] limit the size of the fake stack with a reasonable constant. This fixes a failure when the main thread's stack is considered unlimited (very large).

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190596 91177308-0d34-0410-b5e6-96231b3b80d8
[ASan] Do not build asan_fake_stack_test.cc on OSX until https://code.google.com/p/address-sanitizer/issues/detail?id=222 is fixed.


git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@190597 91177308-0d34-0410-b5e6-96231b3b80d8