[NFC} fix "Target does not support MC emission!" Error in HowToUseJit Example.

[xgupta]

Summary

On running the HowToUseJIT example, after constructing the LLVM module it didn't get JIT compilation instead print the following error message:- Running foo: LLVM ERROR: Target does not support MC emission!
[1] 20154 abort (core dumped) HowToUseJIT.
So this patch fixes the issue and results as expected print 11.

[xgupta]

@lhames Please review the revision and if it looks fine, commit on my behalf as I don't have commit access.

[lhames]

LGTM. Thanks Shivam!

llvm/examples/HowToUseJIT/CMakeLists.txt

   Core
   ExecutionEngine
   Interpreter
+  MC
+  MCJIT
   Support
   nativecodegen
   )

llvm/examples/HowToUseJIT/HowToUseJIT.cpp

 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ExecutionEngine/ExecutionEngine.h"
 #include "llvm/ExecutionEngine/GenericValue.h"
+#include "llvm/ExecutionEngine/MCJIT.h"
 #include "llvm/IR/Argument.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constants.h"

 
 int main() {
   InitializeNativeTarget();
+  LLVMInitializeNativeAsmPrinter();
 
   LLVMContext Context;