[ORC_RT][COFF] Initial platform support for COFF/x86_64.

Initial platform support for COFF/x86_64.

Completed features:
* Statically linked orc runtime.
* Full linking/initialization of static/dynamic vc runtimes and microsoft stl libraries.
* SEH exception handling.
* Full static initializers support
* dlfns
* JIT side symbol lookup/dispatch

Things to note:
* It uses vc runtime libraries found in vc toolchain installations.
* Bootstrapping state is separated because when statically linking orc runtime it needs microsoft stl functions to initialize the orc runtime, but static initializers need to be ran in order to fully initialize stl libraries.
* Process symbols can't be used blidnly on msvc platform; otherwise duplicate definition error gets generated. If process symbols are used, it's destined to get out-of-reach error at some point.
* Atexit currently not handled -- will be handled in the follow-up patches.

Reviewed By: lhames

Differential Revision: https://reviews.llvm.org/D130479

GitOrigin-RevId: 9189a26664b97fdf22c6f7f57194134f707338bc
19 files changed