[MachO] Add a couple of missing braces.
[MachO] Add a couple of missing braces.

Differential Revision:  https://reviews.llvm.org/D21979


git-svn-id: f6089bf0e6284f307027cef4f64114ee9ebb0424@276213 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/lld,llvm-mirror/lld