Only common symbol on MachO and COFF have a size.
For COFF we already had a custom format.
For MachO, there is no native objdump and we were printing it as ELF. Now
we only print the sizes for symbols that actually have them.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240422 91177308-0d34-0410-b5e6-96231b3b80d8