Align the __LD,__compact_unwind section.

I know what would be cool! We should align the compact unwind section because
aligned data access is faster.
<rdar://problem/13723271>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@180171 91177308-0d34-0410-b5e6-96231b3b80d8