[Orc] Remove unnecessary <string> include dependency from Orc headers. NFC.

At most these use the StringRef/Twine wrappers and don't have any implicit uses of std::string.

Move the include down to any cpp implementation where std::string is actually used.

llvm/include/llvm/ExecutionEngine/Orc/CompileOnDemandLayer.h

@@ -47,7 +47,6 @@
 #include <list>
 #include <memory>
 #include <set>
-#include <string>
 #include <utility>
 #include <vector>
 

llvm/include/llvm/ExecutionEngine/Orc/ExecutionUtils.h

@@ -24,7 +24,6 @@
 #include "llvm/Support/DynamicLibrary.h"
 #include <algorithm>
 #include <cstdint>
-#include <string>
 #include <utility>
 #include <vector>
 

llvm/include/llvm/ExecutionEngine/Orc/IRCompileLayer.h

@@ -18,8 +18,9 @@
 #include "llvm/ExecutionEngine/Orc/Layer.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MemoryBuffer.h"
+#include <functional>
 #include <memory>
-#include <string>
+#include <mutex>
 
 namespace llvm {
 

llvm/include/llvm/ExecutionEngine/Orc/IRTransformLayer.h

@@ -17,7 +17,6 @@
 #include "llvm/ExecutionEngine/JITSymbol.h"
 #include "llvm/ExecutionEngine/Orc/Layer.h"
 #include <memory>
-#include <string>
 
 namespace llvm {
 class Module;

llvm/include/llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h

@@ -27,7 +27,6 @@
 #include <functional>
 #include <list>
 #include <memory>
-#include <string>
 #include <utility>
 #include <vector>
 

llvm/include/llvm/ExecutionEngine/Orc/ObjectTransformLayer.h

@@ -17,7 +17,6 @@
 #include "llvm/ExecutionEngine/Orc/Layer.h"
 #include <algorithm>
 #include <memory>
-#include <string>
 
 namespace llvm {
 namespace orc {

llvm/include/llvm/ExecutionEngine/Orc/RTDyldObjectLinkingLayer.h

@@ -28,7 +28,6 @@
 #include <functional>
 #include <list>
 #include <memory>
-#include <string>
 #include <utility>
 #include <vector>
 

llvm/lib/ExecutionEngine/Orc/CompileOnDemandLayer.cpp

@@ -7,12 +7,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ExecutionEngine/Orc/CompileOnDemandLayer.h"
-
 #include "llvm/ADT/Hashing.h"
 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/FormatVariadic.h"
+#include <string>
 
 using namespace llvm;
 using namespace llvm::orc;

llvm/lib/ExecutionEngine/Orc/ExecutionUtils.cpp

@@ -7,7 +7,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ExecutionEngine/Orc/ExecutionUtils.h"
-
 #include "llvm/ExecutionEngine/Orc/Layer.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
@@ -17,6 +16,7 @@
 #include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Target/TargetMachine.h"
+#include <string>
 
 namespace llvm {
 namespace orc {

llvm/lib/ExecutionEngine/Orc/ObjectLinkingLayer.cpp

@@ -7,12 +7,11 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ExecutionEngine/Orc/ObjectLinkingLayer.h"
-
 #include "llvm/ADT/Optional.h"
 #include "llvm/ExecutionEngine/JITLink/EHFrameSupport.h"
 #include "llvm/ExecutionEngine/Orc/DebugObjectManagerPlugin.h"
 #include "llvm/Support/MemoryBuffer.h"
-
+#include <string>
 #include <vector>
 
 #define DEBUG_TYPE "orc"

llvm/unittests/ExecutionEngine/Orc/RTDyldObjectLinkingLayerTest.cpp

@@ -15,6 +15,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/LLVMContext.h"
 #include "gtest/gtest.h"
+#include <string>
 
 using namespace llvm;
 using namespace llvm::orc;