[ELF] Add DebugInfoDWARF dependency

rL284708 introduces a link error when building with BUILD_SHARED_LIBS:

undefined reference to `llvm::DWARFContext::parseCompileUnits()'
undefined reference to `llvm::DWARFContextInMemory::DWARFContextInMemory(
                            llvm::object::ObjectFile const&,
                            llvm::LoadedObjectInfo const*)'
The functions are available in libDebugInfoDWARF, from llvm.

Patch by Visoiu Mistrih Francis

Differential revision: https://reviews.llvm.org/D25843

llvm-svn: 284810