Make the Mac build work.

tools/gn/ninja_helper.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_helper.h"
 
 #include "base/logging.h"
 #include "tools/gn/filesystem_utils.h"
 #include "tools/gn/string_utils.h"
 #include "tools/gn/target.h"
 
 namespace {
 
-const char kLibDirWithSlash[] = "lib";
+const char kLibDirWithSlash[] = "lib/";
 const char kObjectDirNoSlash[] = "obj";
 
 }  // namespace
 
 NinjaHelper::NinjaHelper(const BuildSettings* build_settings)
     : build_settings_(build_settings) {
   build_to_src_no_last_slash_ = build_settings->build_to_source_dir_string();
   if (!build_to_src_no_last_slash_.empty() &&
       build_to_src_no_last_slash_[build_to_src_no_last_slash_.size() - 1] ==
           '/')
@@ skipping 84 matching lines @@
 
 OutputFile NinjaHelper::GetTargetOutputFile(const Target* target) const {
   OutputFile ret;
   if (target->output_type() == Target::NONE) {
     NOTREACHED();
     return ret;
   }
 
   // This is prepended to the output file name.
   const char* prefix;
-  if (target->settings()->IsWin()) {
+  if (target->settings()->IsWin() ||
+      target->output_type() == Target::EXECUTABLE) {
     prefix = "";
   } else {
     prefix = "lib";
   }
 
   const char* extension;
   if (target->output_type() == Target::NONE ||
       target->output_type() == Target::COPY_FILES ||
       target->output_type() == Target::CUSTOM) {
     extension = "stamp";
@@ skipping 42 matching lines @@
   ret.value().append(kObjectDirNoSlash);
   AppendStringPiece(&ret.value(),
                     target->label().dir().SourceAbsoluteWithOneSlash());
   ret.value().append(target->label().name());
   if (extension[0]) {
     ret.value().push_back('.');
     ret.value().append(extension);
   }
   return ret;
 }