Add GN build file for src/sdch

tools/gn/secondary/sdch/BUILD.gn

-# 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.
-
-config("sdch_config") {
-  include_dirs = [ "open-vcdiff/src" ]
-}
-
-static_library("sdch") {
-  sources = [
-    "open-vcdiff/src/addrcache.cc",
-    "open-vcdiff/src/blockhash.cc",
-    "open-vcdiff/src/blockhash.h",
-    "open-vcdiff/src/checksum.h",
-    "open-vcdiff/src/codetable.cc",
-    "open-vcdiff/src/codetable.h",
-    "open-vcdiff/src/compile_assert.h",
-    "open-vcdiff/src/decodetable.cc",
-    "open-vcdiff/src/decodetable.h",
-    "open-vcdiff/src/encodetable.cc",
-    "open-vcdiff/src/encodetable.h",
-    "open-vcdiff/src/google/output_string.h",
-    "open-vcdiff/src/google/vcdecoder.h",
-    "open-vcdiff/src/headerparser.cc",
-    "open-vcdiff/src/headerparser.h",
-    "open-vcdiff/src/instruction_map.cc",
-    "open-vcdiff/src/instruction_map.h",
-    "open-vcdiff/src/logging.cc",
-    "open-vcdiff/src/logging.h",
-    "open-vcdiff/src/rolling_hash.h",
-    "open-vcdiff/src/testing.h",
-    "open-vcdiff/src/varint_bigendian.cc",
-    "open-vcdiff/src/varint_bigendian.h",
-    "open-vcdiff/src/vcdecoder.cc",
-    "open-vcdiff/src/vcdiff_defs.h",
-    "open-vcdiff/src/vcdiffengine.cc",
-    "open-vcdiff/src/vcdiffengine.h",
-    "open-vcdiff/vsprojects/config.h",
-    "open-vcdiff/vsprojects/stdint.h",
-  ]
-
-  direct_dependent_configs = [ ":sdch_config" ]
-
-  if (is_linux || is_android) {
-    include_dirs = [ "linux" ]
-  } else if (is_ios) {
-    include_dirs = [ "ios" ]
-  } else if (is_mac) {
-    include_dirs = [ "mac" ]
-  } else if (is_win) {
-    include_dirs = [ "win" ]
-  }
-
-  deps = [ "//third_party/zlib" ]
-
-  if (is_clang) {
-    cflags = [
-      # TODO(mostynb): remove this if open-vcdiff is ever updated for c++11:
-      "-Wno-deprecated-declarations",
-    ]
-  }
-}