[ORC] Add an 'intern' method to ExecutionEngine for interning symbol names.

This cuts down on boilerplate by reducing 'ES.getSymbolStringPool().intern(...)'
to 'ES.intern(...)'.

llvm-svn: 343427
diff --git a/llvm/unittests/ExecutionEngine/Orc/RTDyldObjectLinkingLayer2Test.cpp b/llvm/unittests/ExecutionEngine/Orc/RTDyldObjectLinkingLayer2Test.cpp
index d5d15b5..1dbd48b 100644
--- a/llvm/unittests/ExecutionEngine/Orc/RTDyldObjectLinkingLayer2Test.cpp
+++ b/llvm/unittests/ExecutionEngine/Orc/RTDyldObjectLinkingLayer2Test.cpp
@@ -52,7 +52,7 @@
 
   ExecutionSession ES;
   auto &JD = ES.createJITDylib("main");
-  auto Foo = ES.getSymbolStringPool().intern("foo");
+  auto Foo = ES.intern("foo");
 
   RTDyldObjectLinkingLayer2 ObjLayer(ES, [&DebugSectionSeen](VModuleKey) {
     return llvm::make_unique<MemoryManagerWrapper>(DebugSectionSeen);
@@ -150,7 +150,7 @@
   // Create a simple stack and set the override flags option.
   ExecutionSession ES;
   auto &JD = ES.createJITDylib("main");
-  auto Foo = ES.getSymbolStringPool().intern("foo");
+  auto Foo = ES.intern("foo");
   RTDyldObjectLinkingLayer2 ObjLayer(
       ES, [](VModuleKey) { return llvm::make_unique<SectionMemoryManager>(); });
   IRCompileLayer2 CompileLayer(ES, ObjLayer, FunkySimpleCompiler(*TM));
@@ -212,7 +212,7 @@
   // Create a simple stack and set the override flags option.
   ExecutionSession ES;
   auto &JD = ES.createJITDylib("main");
-  auto Foo = ES.getSymbolStringPool().intern("foo");
+  auto Foo = ES.intern("foo");
   RTDyldObjectLinkingLayer2 ObjLayer(
       ES, [](VModuleKey) { return llvm::make_unique<SectionMemoryManager>(); });
   IRCompileLayer2 CompileLayer(ES, ObjLayer, FunkySimpleCompiler(*TM));