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 297 matching lines @@
     tool("alink") {
       rspfile = "{{output}}.rsp"
       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 a different wrapper and slightly different command for AIX.
+        ar_wrapper = rebase_path("//build/toolchain/gcc_ar_wrapper_aix.py",

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

Maybe pull out the two differences (ar_wrapper, operation) into variables and
then have the command-variable line only once?

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

Done. Also using the same gcc_ar_wrapper.py instead of having a separate one for
Aix.

+                                 root_build_dir)
+        command = "$python_path \"$ar_wrapper\"$whitelist_flag --output={{output}} --ar=\"$ar\" {{arflags}} rcsT  @\"$rspfile\""
+      } else {
+        ar_wrapper =
+            rebase_path("//build/toolchain/gcc_ar_wrapper.py", root_build_dir)
+        command = "$python_path \"$ar_wrapper\"$whitelist_flag --output={{output}} --ar=\"$ar\" {{arflags}} rcsD @\"$rspfile\""
+      }
+
       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}} $libs_section_postfix"
+      if (current_os == "aix") {
+        # the "--start-group .. --end-group" feature isn't available on the aix ld
+        link_command = "$ld {{ldflags}}${extra_ldflags} -o \"$unstripped_outfile\" @\"$rspfile\" {{solibs}}  $libs_section_prefix {{libs}} $libs_section_postfix"
+      } else {
+        link_command = "$ld {{ldflags}}${extra_ldflags} -o \"$unstripped_outfile\" -Wl,--start-group @\"$rspfile\" {{solibs}} -Wl,--end-group $libs_section_prefix {{libs}} $libs_section_postfix"

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

nit: Readability: Similar to my comment above, maybe factor out two variables
and have the line for link_command only once? Similar to how the whitelist_flag
variable is used above.

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

Done.

+      }
 
       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
     }
   }
 }