Bypassing LLVM for this has a number of benefits:
1) Laziness support becomes asm-syntax agnostic (previously lazy jitting didn't
work on Windows as the resolver block was in Darwin asm).
2) For cross-process JITs, it allows resolver blocks and trampolines to be
emitted directly in the target process, reducing cross process traffic.
3) It should be marginally faster.
llvm-svn: 251933
