GN: nacl_defines: Drop _BSD_SOURCE, _DEFAULT_SOURCE; conditionalize on OS

build/config/nacl/BUILD.gn

 # Copyright (c) 2014 The Native Client 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/nacl/config.gni")
 
 # Native Client Definitions
 config("nacl_defines") {
-  defines = [
-    "_DEFAULT_SOURCE=1",
-    "_BSD_SOURCE=1",
-    "_POSIX_C_SOURCE=199506",
-    "_XOPEN_SOURCE=600",
-    "_GNU_SOURCE=1",
-    "__STDC_LIMIT_MACROS=1",
-  ]
+  if (is_linux || is_android || is_nacl) {
+    defines = [
+      "_POSIX_C_SOURCE=199506",
+      "_XOPEN_SOURCE=600",
+      "_GNU_SOURCE=1",
+      "__STDC_LIMIT_MACROS=1",
+    ]
+  }
 }
 
 config("nexe_defines") {
   defines = [
     "DYNAMIC_ANNOTATIONS_ENABLED=1",
     "DYNAMIC_ANNOTATIONS_PREFIX=NACL_",
   ]
 }
 
 # The base target that all targets in the NaCl build should depend on.
@@ skipping 59 matching lines @@
     "-Os",
 
     # These are omitted from non-IRT libraries to keep the libraries
     # themselves small.
     "-ffunction-sections",
     "-fdata-sections",
   ]
 
   ldflags = [ "-Wl,--gc-sections" ]
 }