Don't use --gdb-index for Gold and LLVM 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/chromecast_build.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
 import("//build/toolchain/cc_wrapper.gni")
@@ skipping 1639 matching lines @@
 
     # TODO(thakis): Figure out if there's a way to make this go for 32-bit,
     # currently we get "warning:
     # obj/native_client/src/trusted/service_runtime/sel_asm/nacl_switch_32.o:
     # DWARF info may be corrupt; offsets in a range list entry are in different
     # sections" there.  Maybe just a bug in nacl_switch_32.S.
     # TODO(thakis): Figure out if there's a way to make this go for official
     # builds, currently get
     # "third_party/binutils/Linux_x64/Release/bin/ld.gold: warning:
     # /tmp/lto-llvm-0b5201.o: corrupt debug info in .debug_info"
+    # TODO(thakis): Figure out how to make this go for Linux ARM64 Debug,

[kjellander_chromium, 2017/04/04 09:06:19]

Are you OK with me assigning a TODO for you? I personally don't know how to fix
this so putting my name in there wouldn't make any sense.

+    # currently get:
+    # /usr/bin/aarch64-linux-gnu-ld: unrecognized option '--gdb-index'
     if (!is_mac && !is_ios && !is_nacl && target_cpu != "x86" &&
+        !(is_linux && target_cpu == "arm64" && is_debug) &&

[Nico, 2017/04/04 13:47:29]

This is because we don't use gold in this config, yeah? Should this be &&
!(use_gold || use_lld)?

[kjellander_chromium, 2017/04/04 14:35:35]

Something along those lines sounds like the proper fix (I guess I'll remove the
TODO in that case).
But both those variables are false for Linux ARM64 Debug, so that will trigger
the same error. Any other suggestion?

[Nico, 2017/04/04 14:50:06]

Oh, I guess I mean (use_gold || use_lld) without the ! (sorry, bools are hard).

[kjellander_chromium, 2017/04/04 14:59:36]

:)
That works much better.

         !allow_posix_link_time_opt && !is_official_build) {
       ldflags += [ "-Wl,--gdb-index" ]
     }
   }
 }
 
 # Minimal symbols.
 config("minimal_symbols") {
   if (is_win) {
     # Linker symbols for backtraces only.
@@ skipping 41 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
   }
 }