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

build/toolchain/gcc_toolchain.gni

 # 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/clang/clang.gni")
 import("//build/config/nacl/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/v8_target_cpu.gni")
 import("//build/toolchain/cc_wrapper.gni")
@@ skipping 299 matching lines @@
       whitelist_flag = " "
       if (enable_resource_whitelist_generation) {
         whitelist_flag = " --resource-whitelist=\"{{output}}.whitelist\""
       }
 
       # This needs a Python script to avoid using simple sh features in this
       # command, in case the host does not use a POSIX shell (e.g. compiling
       # POSIX-like toolchains such as NaCl on Windows).
       ar_wrapper =
           rebase_path("//build/toolchain/gcc_ar_wrapper.py", root_build_dir)
-      command = "$python_path \"$ar_wrapper\"$whitelist_flag --output={{output}} --ar=\"$ar\" {{arflags}} rcsD @\"$rspfile\""
+      if (current_os == "aix") {
+        # We use slightly different arflags for AIX.
+        extra_arflags = "rcsT"
+      } else {
+        extra_arflags = "rcsD"
+      }
+      command = "$python_path \"$ar_wrapper\"$whitelist_flag --output={{output}} --ar=\"$ar\" {{arflags}} $extra_arflags @\"$rspfile\""
       description = "AR {{output}}"
       rspfile_content = "{{inputs}}"
       outputs = [
         "{{output_dir}}/{{target_output_name}}{{output_extension}}",
       ]
 
       # Shared libraries go in the target out directory by default so we can
       # generate different targets with the same name and not have them collide.
       default_output_dir = "{{target_out_dir}}"
       default_output_extension = ".a"
@@ skipping 153 matching lines @@
 
       # Generate a map file to be used for binary size analysis.
       # Map file adds ~10% to the link time on a z620.
       # With target_os="android", libchrome.so.map.gz is ~20MB.
       map_switch = ""
       if (enable_linker_map && is_official_build) {
         map_file = "$unstripped_outfile.map.gz"
         map_switch = " --map-file \"$map_file\""
       }
 
-      link_command = "$ld {{ldflags}}${extra_ldflags} -o \"$unstripped_outfile\" -Wl,--start-group @\"$rspfile\" {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"
+      start_group_flag = " "

[Michael Achenbach, 2017/04/25 14:08:30]

nit: Why not empty string?

[rayb, 2017/04/25 17:28:49]

That was a mistake. Fixed it.

+      end_group_flag = " "
+      if (current_os != "aix") {
+        # the "--start-group .. --end-group" feature isn't available on the aix ld.
+        start_group_flag = "-Wl,--start-group"
+        end_group_flag = "-Wl,--end-group "
+      }
+      link_command = "$ld {{ldflags}}${extra_ldflags} -o \"$unstripped_outfile\" $start_group_flag @\"$rspfile\" {{solibs}} $end_group_flag $libs_section_prefix {{libs}} $libs_section_postfix"
 
       strip_switch = ""
+
       if (defined(invoker.strip)) {
         strip_switch = " --strip=\"${invoker.strip}\" --unstripped-file=\"$unstripped_outfile\""
       }
 
       link_wrapper =
           rebase_path("//build/toolchain/gcc_link_wrapper.py", root_build_dir)
       command = "$python_path \"$link_wrapper\" --output=\"$outfile\"$strip_switch$map_switch -- $link_command"
       description = "LINK $outfile"
       rspfile_content = "{{inputs}}"
       outputs = [
@@ skipping 57 matching lines @@
                            ])
 
     toolchain_args = {
       if (defined(invoker.toolchain_args)) {
         forward_variables_from(invoker.toolchain_args, "*")
       }
       is_clang = true
     }
   }
 }