G M: minor fix to silence warning in cmake version 2.8.11.20130809-gba97e.
G M: minor fix to silence warning in cmake version 2.8.11.20130809-gba97e.

git-svn-id: 756ef344af921d95d562d9e9f9389127a89a6314@188712 91177308-0d34-0410-b5e6-96231b3b80d8

llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx,llvm-mirror/libcxx