Fix nan definition on GN Android 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/sysroot.gni")
 
 # compiler ---------------------------------------------------------------------
 #
 # Base compiler configuration.
@@ skipping 273 matching lines @@
       "UNICODE",
     ]
   }
 
   # Stlport setup. Android uses a different (smaller) version of the STL.
   if (is_android) {
     if (is_clang) {
       # Work around incompatibilities between bionic and clang headers.
       defines += [
         "__compiler_offsetof=__builtin_offsetof",
-        "-Dnan=__builtin_nan",
+        "nan=__builtin_nan",
       ]
     }
 
     defines += [
       "USE_STLPORT=1",
       "_STLP_USE_PTR_SPECIALIZATIONS=1",
       "__GNU_SOURCE=1",  # Necessary for clone().
     ]
 
     ldflags += [
@@ skipping 291 matching lines @@
   } else {
     cflags = [ "-g1" ]
   }
 }
 
 config("no_symbols") {
   if (!is_win) {
     cflags = [ "-g0" ]
   }
 }