WasmObjectWriter mostly operates with function segments offsets that do
not include their size fields. WasmObjectFile needs to have and provide
this information to the lld to maintain proper
R_WEBASSEMBLY_FUNCTION_OFFSET_I32 relocations entries.
Patch by Yury Delendik
Differential Revision: https://reviews.llvm.org/D46763
llvm-svn: 332406