Implement arflags in the GN build.

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")
 import("//build/toolchain/toolchain.gni")
@@ skipping 399 matching lines @@
     }
 
     # Allows the linker to apply ICF to the LTO object file. Also, when
     # targeting ARM, without this flag, LTO produces a .text section that is
     # larger than the maximum call displacement, preventing the linker from
     # relocating calls (http://llvm.org/PR22999).
     if (is_linux) {
       ldflags += [ "-Wl,-plugin-opt,-function-sections" ]
     }
 
+    arflags = [
+      "--plugin",
+      rebase_path("//third_party/llvm-build/Release+Asserts/lib/LLVMgold.so",
+                  root_build_dir),
+    ]

[brucedawson, 2016/04/19 20:59:32]

This arflags initialization is under "if (!is_debug &&
(allow_posix_link_time_opt || is_cfi) && !is_nacl)" whereas before the
equivalent check was under "if ((allow_posix_link_time_opt || is_cfi) &&
invoker.toolchain_os != "nacl")" - the "if (!is_debug" check is new.

Can you confirm that this is intentional or benign?

+
     # TODO(pcc): Make these flags work correctly with CFI.
     if (!is_cfi) {
       cflags += [
         "-fwhole-program-vtables",
 
         # TODO(pcc): Remove this flag once the upstream interface change
         # (http://reviews.llvm.org/D18635) lands.
         "-fwhole-program-vtables-blacklist=" +
             rebase_path("//tools/cfi/blacklist.txt", root_build_dir),
       ]
@@ skipping 970 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
   }
 }