[ELF][LTO][NPM] Use NPM with ENABLE_EXPERIMENTAL_NEW_PASS_MANAGER

[MaskRay]

Looks great!

lld/ELF/Driver.cpp

 #include "lld/Common/Filesystem.h"
 #include "lld/Common/Memory.h"
 #include "lld/Common/Strings.h"
 #include "lld/Common/TargetOptionsCommandFlags.h"
 #include "lld/Common/Version.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringSwitch.h"
+#include "llvm/Config/llvm-config.h"
 #include "llvm/LTO/LTO.h"
 #include "llvm/Remarks/HotnessThresholdParser.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/GlobPattern.h"
 #include "llvm/Support/LEB128.h"
 #include "llvm/Support/Parallel.h"
 #include "llvm/Support/Path.h"
static void readConfigs(opt::InputArgList &args) {
   config->ignoreFunctionAddressEquality =
       args.hasArg(OPT_ignore_function_address_equality);
   config->init = args.getLastArgValue(OPT_init, "_init");
   config->ltoAAPipeline = args.getLastArgValue(OPT_lto_aa_pipeline);
   config->ltoCSProfileGenerate = args.hasArg(OPT_lto_cs_profile_generate);
   config->ltoCSProfileFile = args.getLastArgValue(OPT_lto_cs_profile_file);
   config->ltoDebugPassManager = args.hasArg(OPT_lto_debug_pass_manager);
   config->ltoEmitAsm = args.hasArg(OPT_lto_emit_asm);
-  config->ltoNewPassManager = args.hasFlag(OPT_lto_new_pass_manager,
-                                           OPT_no_lto_new_pass_manager, false);
+  config->ltoNewPassManager =
+      args.hasFlag(OPT_lto_new_pass_manager, OPT_no_lto_new_pass_manager,
+                   LLVM_ENABLE_NEW_PASS_MANAGER);
   config->ltoNewPmPasses = args.getLastArgValue(OPT_lto_newpm_passes);
   config->ltoWholeProgramVisibility =
       args.hasFlag(OPT_lto_whole_program_visibility,
                    OPT_no_lto_whole_program_visibility, false);
   config->ltoo = args::getInteger(args, OPT_lto_O, 2);
   config->ltoObjPath = args.getLastArgValue(OPT_lto_obj_path_eq);
   config->ltoPartitions = args::getInteger(args, OPT_lto_partitions, 1);
   config->ltoSampleProfile = args.getLastArgValue(OPT_lto_sample_profile);