For building v8 using gn on aix_ppc64, linux_s390x and linux_ppc64.

build/config/features.gni

 # Copyright 2014 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.
 
 # =============================================
 #   PLEASE DO NOT ADD MORE FLAGS TO THIS FILE
 # =============================================
 #
 # These flags are effectively global. Your feature flag should go near the
 # code it controls. Most of these items are here now because they control
 # legacy global #defines passed to the compiler (now replaced with generated
 # buildflag headers -- see //build/buildflag_header.gni).
 #
 # There is more advice on where to put build flags in the "Build flag" section
 # of //build/config/BUILDCONFIG.gn.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 if (is_android) {
   import("//build/config/android/config.gni")
 }
 
 declare_args() {
   # Enables Native Client support.
   # Temporarily disable nacl on arm64 linux to get rid of compilation errors.
   # TODO(mcgrathr): When mipsel-nacl-clang is available, drop the exclusion.
-  enable_nacl = !is_ios && !is_android && !is_chromecast &&
-                current_cpu != "mipsel" && !(is_linux && target_cpu == "arm64")
+  enable_nacl =
+      !is_ios && !is_android && !is_chromecast && current_os != "aix" &&
+      current_cpu != "mipsel" && !(is_linux && target_cpu == "arm64") &&
+      (current_cpu != "s390" && current_cpu != "s390x" &&

[Michael Achenbach, 2017/04/18 13:46:04]

nit: Why parentheses?

[rayb, 2017/04/25 00:41:04]

Done.

+       target_cpu != "s390" && target_cpu != "s390x") &&
+      (current_cpu != "ppc" && current_cpu != "ppc64" && target_cpu != "ppc" &&
+       target_cpu != "ppc64")

[Dirk Pranke, 2017/04/14 01:29:02]

Are you planning to port NaCl to these architectures? I'm guessing not, and
maybe we can just simplify this logic to only look at the target_cpus?

[rayb, 2017/04/25 00:41:04]

Not that I know of. Also simplified the logic a little.

 
   # Non-SFI is not yet supported on mipsel
   enable_nacl_nonsfi = current_cpu != "mipsel"
 
   # Enables the Media Router.
   enable_media_router = !is_ios && !is_chromecast
 
   # Enables proprietary codecs and demuxers; e.g. H264, AAC, MP3, and MP4.
   # We always build Google Chrome and Chromecast with proprietary codecs.
   #
@@ skipping 28 matching lines @@
   use_gconf = is_linux && !is_chromeos && !is_chromecast
 
   use_gio = is_linux && !is_chromeos && !is_chromecast
 }
 #
 # =============================================
 #   PLEASE DO NOT ADD MORE FLAGS TO THIS FILE
 # =============================================
 #
 # See comment at the top.