[Orc] Resolve crashes in the examples HowToUsejit and Kaleidoscope-Ch4, Kaleidoscope-Ch5, ..., Kaleidoscope-Ch9

[damian]

Summary

This is my first review!!

When following the tutorial and came to Kaleidoscope chapter4 the code was crashing when running the following code:
def testfunc(x y) x + y*2;
testfunc(4, 10);

I then patched the code:

1. Make sure ForceInterpreterLinking is defined, to avoid an error "interpreter has not been linked".
2. When Finding the symbol we only looked for external functions in Kaleidoscope.

After that the code does on no longer crash.

There is still an issue when entering empty strings, but I a fix for this might come later.

examples/HowToUseJIT/HowToUseJIT.cpp

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

examples/Kaleidoscope/Chapter4/CMakeLists.txt

   Analysis
   Core
   ExecutionEngine
+  Interpreter
   InstCombine
   Object
   OrcJIT

examples/Kaleidoscope/Chapter5/CMakeLists.txt

   Analysis
   Core
   ExecutionEngine
+  Interpreter
   InstCombine
   Object
   OrcJIT

examples/Kaleidoscope/Chapter6/CMakeLists.txt

   Analysis
   Core
   ExecutionEngine
+  Interpreter
   InstCombine
   Object
   OrcJIT

examples/Kaleidoscope/Chapter7/CMakeLists.txt

   Analysis
   Core
   ExecutionEngine
+  Interpreter
   InstCombine
   Object
   OrcJIT

examples/Kaleidoscope/Chapter9/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   Core
   ExecutionEngine
+  Interpreter
   Object
   OrcJIT
   Support

examples/Kaleidoscope/include/KaleidoscopeJIT.h

 #include "llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h"
 #include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
 #include "llvm/ExecutionEngine/SectionMemoryManager.h"
+#include "llvm/ExecutionEngine/Interpreter.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/Support/DynamicLibrary.h"

       : Resolver(createLegacyLookupResolver(
             ES,
             [this](const std::string &Name) {
-              return ObjectLayer.findSymbol(Name, true);
+              return ObjectLayer.findSymbol(Name, false);
             },
             [](Error Err) { cantFail(std::move(Err), "lookupFlags failed"); })),
         TM(EngineBuilder().selectTarget()), DL(TM->createDataLayout()),