GN: Don't write ldflags and libs when unneeded.

tools/gn/ninja_binary_target_writer_unittest.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_binary_target_writer.h"
 
 #include <sstream>
 #include <utility>
 
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 92 matching lines @@
         "defines =\n"
         "include_dirs =\n"
         "root_out_dir = .\n"
         "target_out_dir = obj/foo\n"
         "target_output_name = libstlib\n"
         "\n"
         "\n"
         // There are no sources so there are no params to alink. (In practice
         // this will probably fail in the archive tool.)
         "build obj/foo/libstlib.a: alink || obj/foo/bar.stamp\n"
-        "  ldflags =\n"
-        "  libs =\n"
         "  output_extension = \n";
     std::string out_str = out.str();
     EXPECT_EQ(expected, out_str);
   }
 
   // Make the static library 'complete', which means it should be linked.
   stlib_target.set_complete_static_lib(true);
   {
     std::ostringstream out;
     NinjaBinaryTargetWriter writer(&stlib_target, out);
     writer.Run();
 
     const char expected[] =
         "defines =\n"
         "include_dirs =\n"
         "root_out_dir = .\n"
         "target_out_dir = obj/foo\n"
         "target_output_name = libstlib\n"
         "\n"
         "\n"
         // Ordering of the obj files here should come out in the order
         // specified, with the target's first, followed by the source set's, in
         // order.
         "build obj/foo/libstlib.a: alink obj/foo/bar.input1.o "
             "obj/foo/bar.input2.o ../../foo/input3.o ../../foo/input4.obj "
             "|| obj/foo/bar.stamp\n"
-        "  ldflags =\n"
-        "  libs =\n"
         "  output_extension = \n";
     std::string out_str = out.str();
     EXPECT_EQ(expected, out_str);
   }
 }
 
 // This tests that output extension overrides apply, and input dependencies
 // are applied.
 TEST(NinjaBinaryTargetWriter, ProductExtensionAndInputDeps) {
   TestWithScope setup;
@@ skipping 577 matching lines @@
 
   EXPECT_FALSE(scheduler.is_failed());
 
   std::ostringstream out;
   NinjaBinaryTargetWriter writer(&target, out);
   writer.Run();
 
   // Should have issued an error.
   EXPECT_TRUE(scheduler.is_failed());
 }