[libunwind] Fix Unwind-EHABI.cpp:getByte on big-endian targets
[libunwind] Fix Unwind-EHABI.cpp:getByte on big-endian targets

Summary:
The function getByte is dependent on endianness and the current
behavior is incorrect on big-endian targets.

This patch fixes the issue.

Reviewers: phosek, ostannard, dmgreen, christof, chill

Reviewed By: ostannard, chill

Subscribers: chill, christof, libcxx-commits

Tags: #libc

Differential Revision: https://reviews.llvm.org/D64402

git-svn-id: 62ef012455b6b8fcec9c41ca270ebf409aae1006@365505 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libunwind,llvm-mirror/libunwind,llvm-mirror/libunwind