Make __DATE__ and __TIME__ to evaluate to an empty string.

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 148 matching lines @@
     ":compiler_cpu_abi",
     ":compiler_codegen",
   ]
 
   # In general, Windows is totally different, but all the other builds share
   # some common GCC configuration.
   if (!is_win) {
     # Common GCC compiler flags setup.
     # --------------------------------
     cflags += [ "-fno-strict-aliasing" ]  # See http://crbug.com/32204
+
+    # Eliminate build metadata (__DATE__ and __TIME_) for deterministic build.
+    # See https://crbug.com/314403
+    cflags += [
+      "-Wno-builtin-macro-redefined",

[Nico, 2016/08/24 14:41:12]

This looks pretty hacky. Can we instead teach the compiler real support for
this?

+      "-D__DATE__=",

[Nico, 2016/08/24 14:41:12]

__DATE__ and __TIME__ are supposed to be string constants. Instead of defining
them to nothing, at least define them to "", which will likely fix the ios bot.
But even then, they'll have a weird length, so maybe consider defining them to
"Oct 09 2008" and "12:34:56"

+      "-D__TIME__=",
+    ]
+
     cflags_cc += [
       # If this is removed then remove the corresponding /Zc:threadSafeInit- for
       # Windows.
       "-fno-threadsafe-statics",
 
       # Not exporting C++ inline functions can generally be applied anywhere
       # so we do so here. Normal function visibility is controlled by
       # //build/config/gcc:symbol_visibility_hidden.
       "-fvisibility-inlines-hidden",
     ]
@@ skipping 1402 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
   }
 }