[WebAssembly] MC: Don't allow zero sized data segments

This ensures that each segment has a unique address.
Without this, consecutive zero sized symbols would
end up with the same address and the linker cannot
map symbols to unique data segments.

Differential Revision: https://reviews.llvm.org/D39107

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@316717 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed