Fix "undefined reference to '__atomic_is_lock_free'" errors on Linux

base/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.
 
 # HOW TO WRITE CONDITIONALS IN THIS FILE
 # ======================================
 #
 # In many other places, one would write a conditional that expresses all the
 # cases when a source file is used or unused, and then either add or subtract
 # it from the sources list in that case
 #
 # Since base includes so many low-level things that vary widely and
 # unpredictably for the various build types, we prefer a slightly different
 # style. Instead, there are big per-platform blocks of inclusions and
 # exclusions. If a given file has an inclusion or exclusion rule that applies
 # for multiple conditions, perfer to duplicate it in both lists. This makes it
 # a bit easier to see which files apply in which cases rather than having a
 # huge sequence of random-looking conditionals.
 
 import("//build/buildflag_header.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/nacl/config.gni")
+import("//build/config/sysroot.gni")
 import("//build/config/ui.gni")
 import("//build/nocompile.gni")
 import("//testing/test.gni")
 
 declare_args() {
   # Override this value to give a specific build date.
   # See //base/build_time.cc for more details.
   override_build_date = "N/A"
 }
 
@@ skipping 940 matching lines @@
     "//third_party/modp_b64",
   ]
 
   public_deps = [
     ":base_paths",
     ":base_static",
     ":build_date",
     ":debugging_flags",
   ]
 
+  # Needed for <atomic> if using newer C++ library than sysroot
+  if (!use_sysroot && (is_android || is_linux)) {
+    libs = [ "atomic" ]
+  }
+
   # Allow more direct string conversions on platforms with native utf8
   # strings
   if (is_mac || is_ios || is_chromeos) {
     defines += [ "SYSTEM_NATIVE_UTF8" ]
   }
 
   # Android.
   if (is_android) {
     sources -= [
       "debug/stack_trace_posix.cc",
@@ skipping 1089 matching lines @@
 
   # GYP: //base.gyp:base_java_unittest_support
   android_library("base_java_unittest_support") {
     deps = [
       ":base_java",
     ]
     java_files =
         [ "test/android/java/src/org/chromium/base/ContentUriTestUtils.java" ]
   }
 }