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

build/toolchain/gcc_toolchain.gni

Index: build/toolchain/gcc_toolchain.gni
diff --git a/build/toolchain/gcc_toolchain.gni b/build/toolchain/gcc_toolchain.gni
index dfd187954cd148c690223a913eeac524a85e269c..0badd7ea2988cdcbb06542548aa60859819a8d8d 100644
--- a/build/toolchain/gcc_toolchain.gni
+++ b/build/toolchain/gcc_toolchain.gni
@@ -315,9 +315,17 @@ template("gcc_toolchain") {
       # 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 = [
@@ -491,9 +499,15 @@ template("gcc_toolchain") {
         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\""
       }