[llvm-lto2] Use NPM with ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER

[tejohnson]

lgtm

llvm/tools/llvm-lto2/llvm-lto2.cpp

 //
 // This program is intended to eventually replace llvm-lto which uses the legacy
 // LTO interface.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/CodeGen/CommandFlags.h"
+#include "llvm/Config/llvm-config.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/LTO/Caching.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/Passes/PassPlugin.h"
 #include "llvm/Remarks/HotnessThresholdParser.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/InitLLVM.h"

 static cl::opt<bool>
     RunCSIRInstr("lto-cspgo-gen",
                  cl::desc("Run PGO context sensitive IR instrumentation"),
                  cl::init(false), cl::Hidden);
 
 static cl::opt<bool>
     UseNewPM("use-new-pm",
              cl::desc("Run LTO passes using the new pass manager"),
-             cl::init(false), cl::Hidden);
+             cl::init(LLVM_ENABLE_NEW_PASS_MANAGER), cl::Hidden);
 
 static cl::opt<bool>
     DebugPassManager("debug-pass-manager", cl::init(false), cl::Hidden,
                      cl::desc("Print pass management debugging information"));
 
 static cl::opt<std::string>
     StatsFile("stats-file", cl::desc("Filename to write statistics to"));