add --gdb-index to linker

build/config/compiler/BUILD.gn

 # Copyright (c) 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/config.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
 
@@ skipping 57 matching lines @@
   if (is_win) {
     # Whether the VS xtree header has been patched to disable warning 4702. If
     # it has, then we don't need to disable 4702 (unreachable code warning).
     # The patch is preapplied to the internal toolchain and hence all bots.
     msvs_xtree_patched = false
   }
 
   # Omit unwind support in official builds to save space.
   # We can use breakpad for these builds.
   exclude_unwind_tables = is_chrome_branded && is_official_build
+
+  # If true, gold linker will save symbol table inside object files.
+  # This speeds up gdb startup by 60%
+  gdb_index = false
 }
 
 # Apply the default logic for these values if they were not set explicitly.
 if (gold_path == false) {
   if (use_gold) {
     gold_path = rebase_path("//third_party/binutils/Linux_x64/Release/bin",
                             root_build_dir)
   } else {
     gold_path = ""
   }
@@ skipping 192 matching lines @@
       # saved ~20% of link time.
       # https://groups.google.com/a/chromium.org/group/chromium-dev/browse_thread/thread/281527606915bb36
       # Only apply this to the target linker, since the host
       # linker might not be gold, but isn't used much anyway.
       # TODO(raymes): Disable threading because gold is frequently
       # crashing on the bots: crbug.com/161942.
       #"-Wl,--threads",
       #"-Wl,--thread-count=4",
     ]
 
+    if (gdb_index) {
+      ldflags += [ "-Wl,--gdb-index" ]
+    }
+
     if (!using_sanitizer && !(is_android && use_order_profiling)) {
       # TODO(brettw) common.gypi has this only for target toolset.
       ldflags += [ "-Wl,--icf=all" ]
     }
 
     # TODO(thestig): Make this flag work with GN.
     #if (!is_official_build && !is_chromeos && !(is_asan || is_lsan || is_tsan || is_msan)) {
     #  ldflags += [
     #    "-Wl,--detect-odr-violations",
     #  ]
@@ skipping 1038 matching lines @@
 
 if (is_ios || is_mac) {
   # On Mac and iOS, this enables support for ARC (automatic ref-counting).
   # See http://clang.llvm.org/docs/AutomaticReferenceCounting.html.
   config("enable_arc") {
     common_flags = [ "-fobjc-arc" ]
     cflags_objc = common_flags
     cflags_objcc = common_flags
   }
 }