[BOLT] Fix ORC to properly update symbols

Summary:
In new ORC, the sequence of how sections are allocated and loaded is
changed. Now everything is delayed until emitAndFinalize() is called,
and all actions are supposed to happen via notification functors.
There are two functors that we pass to new ObjectLinkingLayer object.
One is used to notify when objects are loaded, and the other - once they
are finalized. We use the first one to remap sections to proper
addresses, and that's the earliest place where we can do it. However,
ORC decides to update symbols right before that, and as a result they
are updated with non-mapped values.

There are two possible fixes for that. This diff postpones the update to
the symbol table until the notifier is called. I don't know what other
tools depend on the existing sequence, and the proper fix may involve
creating a third notifier to be called before the symbol table update.

(cherry picked from FBD7280973)