[LLVM][RUNTIME] Add optional LLVM ORCJIT runtime executor

[cbalint13]

This PR introduce a new LLVM ORC JIT executor for the runtime. The new ORCJIT may obsolete MCJIT due to better upstream maintenance.

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Changes

• Old MCJIT is default , thus the previous behaviour is unchanged.
• The new ORCJIT is added as a alternative and optional llvm runtime engine.

Rationale

• MCJIT is the first implementation in LLVM and looks to be unmaintained by upstream.
• The new ORCJIT is added and it shares the same flow configuration as the current MCJIT.
• Targets like RISCV, and possible others too, will not work on MCJIT see some discussions here .
• The new ORCJIT offers flexibile custom compilation and linkage flow that can be useful for future challenges.

Usage

• The default is the old MCJIT so no changes in any behaviour of TVM, but being limited it fails on e.g. RISCV:

[23:35:43] src/target/llvm/codegen_llvm.cc:185: Warning: Set native vector bits to be 128 for riscv64
LLVM ERROR: Relocation type not implemented yet!

• The new ORCJIT can be invoked by llvm -jit=orcjit {...}, this works even on RISCV targets.

This implementation here is backward compatibile and was tested on LLVM={10,11,12,13,14,15,16,17,18}

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Halide project also leverage orcjit runtime. Also may relate to PR https://github.com/apache/tvm/pull/14836 and TK #10141 ongoing effort toward RISCV tensorization.

[cbalint13]

This is ready for review. Cc: @Lunderberg , @junrushao , @masahi , @vinx13, @tqchen , @ekalda , @lhutton1 , @quic-sanirudh , @kparzysz-quic Cc: @katebern-grovety , @PhilippvK

[tqchen]

@cbalint13 do you mind to rebase on latest main? love to get it in

[cbalint13]

@tqchen

@cbalint13 do you mind to rebase on latest main? love to get it in

It is rebased now, glad to see it as being useful. Thank you !