GN: Avoid nontrivial shell commands in gcc_toolchain tools

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/nacl/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/toolchain/ccache.gni")
 import("//build/toolchain/goma.gni")
 import("//build/toolchain/toolchain.gni")
 
@@ skipping 196 matching lines @@
 
     tool("alink") {
       rspfile = "{{output}}.rsp"
       arflags = ""
       if (is_cfi && invoker.toolchain_os != "nacl") {
         gold_plugin_path = rebase_path(
                 "//third_party/llvm-build/Release+Asserts/lib/LLVMgold.so",
                 root_build_dir)
         arflags = "--plugin $gold_plugin_path"
       }
-      command = "rm -f {{output}} && $ar rcs $arflags {{output}} @$rspfile"
+
+      # 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. Windows).
+      ar_wrapper = rebase_path("//build/toolchain/gcc_ar_wrapper.py")
+      command = "$python_path $ar_wrapper --output={{output}} --ar=$ar $arflags rcs @$rspfile"
       description = "AR {{output}}"
       rspfile_content = "{{inputs}}"
       outputs = [
         "{{target_out_dir}}/{{target_output_name}}{{output_extension}}",
       ]
       default_output_extension = ".a"
       output_prefix = "lib"
     }
 
     tool("solink") {
       soname = "{{target_output_name}}{{output_extension}}"  # e.g. "libfoo.so".
       sofile = "{{root_out_dir}}/$soname"  # Possibly including toolchain dir.
       if (shlib_subdir != ".") {
         sofile = "{{root_out_dir}}/$shlib_subdir/$soname"
       }
       rspfile = sofile + ".rsp"
 
       unstripped_sofile = sofile
       if (defined(invoker.strip)) {
         unstripped_sofile = "{{root_out_dir}}/lib.unstripped/$soname"
       }
 
-      # These variables are not built into GN but are helpers that implement
-      # (1) linking to produce a .so, (2) extracting the symbols from that file
-      # to a temporary file, (3) if the temporary file has differences from the
-      # existing .TOC file, overwrite it, otherwise, don't change it.
+      # These variables are not built into GN but are helpers that
+      # implement (1) linking to produce a .so, (2) extracting the symbols
+      # from that file (3) if the extracted list differs from the existing
+      # .TOC file, overwrite it, otherwise, don't change it.
       tocfile = sofile + ".TOC"
-      temporary_tocname = sofile + ".tmp"
 
       link_command = "$ld -shared {{ldflags}} -o $unstripped_sofile -Wl,-soname=$soname @$rspfile"
+
       assert(defined(readelf), "to solink you must have a readelf")
       assert(defined(nm), "to solink you must have an nm")
-      toc_command = "{ $readelf -d $unstripped_sofile | grep SONAME ; $nm -gD -f p $unstripped_sofile | cut -f1-2 -d' '; } > $temporary_tocname"
-      replace_command = "if ! cmp -s $temporary_tocname $tocfile; then mv $temporary_tocname $tocfile; fi"
+      strip_switch = ""
+      if (defined(invoker.strip)) {
+        strip_switch = "--strip=${invoker.strip}"
+      }
 
-      command = "$link_command && $toc_command && $replace_command"
-      if (defined(invoker.strip)) {
-        strip_command =
-            "${invoker.strip} --strip-unneeded -o $sofile $unstripped_sofile"
-        command += " && " + strip_command
-      }
+      # This needs a Python script to avoid using a complex shell command
+      # requiring sh control structures, pipelines, and POSIX utilities.
+      # The host might not have a POSIX shell and utilities (e.g. Windows).
+      solink_wrapper = rebase_path("//build/toolchain/gcc_solink_wrapper.py")
+      command = "$python_path $solink_wrapper --readelf=$readelf --nm=$nm $strip_switch --sofile=$unstripped_sofile --tocfile=$tocfile --output=$sofile -- $link_command"
+
       rspfile_content = "-Wl,--whole-archive {{inputs}} {{solibs}} -Wl,--no-whole-archive $solink_libs_section_prefix {{libs}} $solink_libs_section_postfix"
 
       description = "SOLINK $sofile"
 
       # Use this for {{output_extension}} expansions unless a target manually
       # overrides it (in which case {{output_extension}} will be what the target
       # specifies).
       default_output_extension = default_shlib_extension
 
       output_prefix = "lib"
@@ skipping 170 matching lines @@
     nm = "${toolprefix}nm"
 
     forward_variables_from(invoker,
                            [
                              "toolchain_cpu",
                              "toolchain_os",
                              "use_gold",
                            ])
   }
 }