Add librt to default libs on linux

build/config/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/allocator.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/sanitizers/sanitizers.gni")
@@ skipping 370 matching lines @@
   } else if (is_ios) {
     # The libraries listed here will be specified for both the target and the
     # host. Only the common ones should be listed here.
     libs = [
       "CoreFoundation.framework",
       "CoreGraphics.framework",
       "CoreText.framework",
       "Foundation.framework",
     ]
   } else if (is_linux) {
-    libs = [ "dl" ]
+    libs = [
+      "dl",
+      "rt",
+    ]
   }
 }
 
 # Executable configs -----------------------------------------------------------
 
 # Windows linker setup for EXEs and DLLs.
 if (is_win) {
   _windows_linker_configs = [
     "//build/config/win:sdk_link",
     "//build/config/win:common_linker_setup",
@@ skipping 67 matching lines @@
     # This error doesn't happen every time. In VS2013, it seems if the .pch
     # file doesn't exist, no error will be generated (probably MS tested this
     # case but forgot the other one?). To reproduce this error, do a build,
     # then delete the precompile.c.obj file, then build again.
     cflags_c = [ "/wd4206" ]
   } else if (is_mac && !is_official_build && !use_goma) {
     precompiled_header = "build/precompile.h"
     precompiled_source = "//build/precompile.h"
   }
 }