As LLVM Orc v2 API is in flux, changes are being made in google3. This
CL applies those changes, while also continuing to make our backend
work against LLVM 10.

Bug: b/171402030
Change-Id: If7be93bfe495e9d40a6e69415978a622ed3afb50
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/49608
Presubmit-Ready: Antonio Maiorano <amaiorano@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Antonio Maiorano <amaiorano@google.com>