Reapply: [WebAssembly] Implement build-id feature

Implement the --build-id flag similarly to ELF, and generate a
build_id section according to the WebAssembly tool convention
specified in https://github.com/WebAssembly/tool-conventions/pull/183

The default style ("fast" aka "tree") hashes the contents of the
output and (unlike ELF) generates a v5 UUID based on the hash (using a
random namespace). It also supports generating a random v4 UUID, a
sha1 hash, and a user-specified string (as ELF does).

Differential Revision: https://reviews.llvm.org/D107662

Fix MSVC build by std::copy on the underying buffer rather than
directly from std::array to llvm::MutableArrayRef