Support explicit pools in actions

tools/gn/ninja_build_writer.cc

 // 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.
 
 #include "tools/gn/ninja_build_writer.h"
 
 #include <stddef.h>
 
 #include <fstream>
 #include <map>
@@ skipping 267 matching lines @@
   std::unordered_set<const Pool*> used_pools;
   for (const auto& pair : used_toolchains_) {
     for (int j = Toolchain::TYPE_NONE + 1; j < Toolchain::TYPE_NUMTYPES; j++) {
       Toolchain::ToolType tool_type = static_cast<Toolchain::ToolType>(j);
       const Tool* tool = pair.second->GetTool(tool_type);
       if (tool && tool->pool().ptr)
         used_pools.insert(tool->pool().ptr);
     }
   }
 
+  for (const Target* target : default_toolchain_targets_) {
+    if (target->output_type() == Target::ACTION) {
+      const LabelPtrPair<Pool>& pool = target->action_values().pool();
+      if (pool.ptr)
+        used_pools.insert(pool.ptr);
+    }
+  }
+
   // Write pools sorted by their name, to make output deterministic.
   std::vector<const Pool*> sorted_pools(used_pools.begin(), used_pools.end());
   auto pool_name = [this](const Pool* pool) {
     return pool->GetNinjaName(default_toolchain_->label());
   };
   std::sort(sorted_pools.begin(), sorted_pools.end(),
             [&pool_name](const Pool* a, const Pool* b) {
               return pool_name(a) < pool_name(b);
             });
   for (const Pool* pool : sorted_pools) {
@@ skipping 262 matching lines @@
   EscapeOptions ninja_escape;
   ninja_escape.mode = ESCAPE_NINJA;
 
   // Escape for special chars Ninja will handle.
   std::string escaped = EscapeString(phony_name, ninja_escape, nullptr);
 
   out_ << "build " << escaped << ": phony ";
   path_output_.WriteFile(out_, target->dependency_output_file());
   out_ << std::endl;
 }