zorg: use --enable-libcpp on darwin

<rdar://problem/15825712>

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@199330 91177308-0d34-0410-b5e6-96231b3b80d8
zorg: use --enable-libcpp in more places

This is a follow up to r199330.

<rdar://problem/15825712>

git-svn-id: https://llvm.org/svn/llvm-project/zorg/trunk@199331 91177308-0d34-0410-b5e6-96231b3b80d8