[WebAssembly] Improve support for "needed" list in dylink section

This change adds basic support for shared library dependencies
via the dylink section.

See https://github.com/WebAssembly/tool-conventions/pull/77

Differential Revision: https://reviews.llvm.org/D59237

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@356102 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed