[PATCH] [asan] disable fast unwind on ARM

[Kostya Serebryany]

I think this is a mistake.
The slow unwinder is so terribly slow that you will not be able to use asan
on anything other than small test cases.
Instead, you need to make the fast unwinder work by enabling frame pointers
at compile time.
We do it on Android ARM, so I think this can and should be done on Linux
ARM as well.

Note also, that there are run-time flags that control the unwinder:
fast_unwind_on_fatal0Use fast unwinder when found a bug. The fast one
relies on frame pointers, while slow one does not. See also
CallStack<https://code.google.com/p/address-sanitizer/wiki/CallStack>
fast_unwind_on_malloc1Same as fast_unwind_on_fatal, but control unwinding
inside malloc/free, i.e. performance critical. See also
CallStack<https://code.google.com/p/address-sanitizer/wiki/CallStack>
--kcc

http://reviews.llvm.org/D3814