Use llvm::outs for jit.dump machine code

The jit.dump used std::cout previously.  This could cause a problem
when using jit.dump=7 because llvm::outs() for IR and std::cout
for machine code could conflict and the machine code dump could get lost
Merge pull request #3036 from southerngs/llvm_out_machine_code

Use llvm::outs for jit.dump machine code