Fix IOError exception being raised in `asan_symbolize.py`crash when using `atos` symbolizer on Darwin when the binaries don't exist.
Fix IOError exception being raised in `asan_symbolize.py`crash when
using `atos` symbolizer on Darwin when the binaries don't exist.

For now we just produce an unsymbolicated stackframe when the binary
doesn't exist.

git-svn-id: c199f293c43da69278bea8e88f92242bf3aa95f7@348659 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