GN: aix port along with linux_s390x, linux_ppc64 and linux_ppc64le support.

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
@@ skipping 1194 matching lines @@
       ":base_jni_headers",
       "//third_party/android_tools:cpu_features",
       "//third_party/ashmem",
     ]
 
     # Needs to be a public config so that dependent targets link against it as
     # well when doing a component build.
     public_configs = [ ":android_system_libs" ]
   }
 
+  # AIX
+  if (is_aix) {
+    sources += [
+      "base/process/internal_aix.cc",
+      "base/process/internal_aix.h",
+    ]
+  }
+
   # Chromeos.
   if (is_chromeos) {
     sources += [ "power_monitor/power_monitor_device_source_chromeos.cc" ]
   }
 
   # NaCl.
   if (is_nacl) {
     # We reset sources_assignment_filter in order to explicitly include
     # the linux file (which would otherwise be filtered out).
     set_sources_assignment_filter([])
@@ skipping 1470 matching lines @@
 }
 
 fuzzer_test("base_json_correctness_fuzzer") {
   sources = [
     "json/correctness_fuzzer.cc",
   ]
   deps = [
     ":base",
   ]
 }