[WebAssembly] Remove ELF file support.

This support was partial and temporary.  Now that we have
wasm object file support its no longer needed.

Differential Revision: https://reviews.llvm.org/D48744

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@337222 91177308-0d34-0410-b5e6-96231b3b80d8
30 files changed