Remove obsolete OS handling in GN.

tools/gn/ninja_copy_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 <algorithm>
 #include <sstream>
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/ninja_copy_target_writer.h"
 #include "tools/gn/target.h"
 #include "tools/gn/test_with_scope.h"
 
 // Tests multiple files with an output pattern and no toolchain dependency.
 TEST(NinjaCopyTargetWriter, Run) {
   TestWithScope setup;
   Err err;
 
-  setup.settings()->set_target_os(Settings::LINUX);
   setup.build_settings()->SetBuildDir(SourceDir("//out/Debug/"));
   Target target(setup.settings(), Label(SourceDir("//foo/"), "bar"));
   target.set_output_type(Target::COPY_FILES);
 
   target.sources().push_back(SourceFile("//foo/input1.txt"));
   target.sources().push_back(SourceFile("//foo/input2.txt"));
 
   target.action_values().outputs() =
       SubstitutionList::MakeForTest("//out/Debug/{{source_name_part}}.out");
 
@@ skipping 11 matching lines @@
       "build obj/foo/bar.stamp: stamp input1.out input2.out\n";
   std::string out_str = out.str();
   EXPECT_EQ(expected_linux, out_str);
 }
 
 // Tests a single file with no output pattern.
 TEST(NinjaCopyTargetWriter, ToolchainDeps) {
   TestWithScope setup;
   Err err;
 
-  setup.settings()->set_target_os(Settings::LINUX);
   setup.build_settings()->SetBuildDir(SourceDir("//out/Debug/"));
   Target target(setup.settings(), Label(SourceDir("//foo/"), "bar"));
   target.set_output_type(Target::COPY_FILES);
 
   target.sources().push_back(SourceFile("//foo/input1.txt"));
 
   target.action_values().outputs() =
       SubstitutionList::MakeForTest("//out/Debug/output.out");
 
   target.SetToolchain(setup.toolchain());
   ASSERT_TRUE(target.OnResolved(&err));
 
   std::ostringstream out;
   NinjaCopyTargetWriter writer(&target, out);
   writer.Run();
 
   const char expected_linux[] =
       "build output.out: copy ../../foo/input1.txt\n"
       "\n"
       "build obj/foo/bar.stamp: stamp output.out\n";
   std::string out_str = out.str();
   EXPECT_EQ(expected_linux, out_str);
 }
 
 TEST(NinjaCopyTargetWriter, OrderOnlyDeps) {
   TestWithScope setup;
   Err err;
 
-  setup.settings()->set_target_os(Settings::LINUX);
   setup.build_settings()->SetBuildDir(SourceDir("//out/Debug/"));
 
   Target target(setup.settings(), Label(SourceDir("//foo/"), "bar"));
   target.set_output_type(Target::COPY_FILES);
   target.sources().push_back(SourceFile("//foo/input1.txt"));
   target.action_values().outputs() =
       SubstitutionList::MakeForTest("//out/Debug/{{source_name_part}}.out");
   target.inputs().push_back(SourceFile("//foo/script.py"));
   target.SetToolchain(setup.toolchain());
   ASSERT_TRUE(target.OnResolved(&err));
 
   std::ostringstream out;
   NinjaCopyTargetWriter writer(&target, out);
   writer.Run();
 
   const char expected_linux[] =
       "build obj/foo/bar.inputdeps.stamp: stamp ../../foo/script.py\n"
       "build input1.out: copy ../../foo/input1.txt || "
           "obj/foo/bar.inputdeps.stamp\n"
       "\n"
       "build obj/foo/bar.stamp: stamp input1.out\n";
   std::string out_str = out.str();
   EXPECT_EQ(expected_linux, out_str);
 }