Convert third_party source sets to static libraries.

third_party/opus/BUILD.gn

 # Copyright 2014 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.
 
 import("//build/config/arm.gni")
 import("//testing/test.gni")
 
 # If fixed point implementation shall be used (otherwise float).
 use_opus_fixed_point = current_cpu == "arm" || current_cpu == "arm64"
 
@@ skipping 45 matching lines @@
   }
 }
 
 config("opus_warnings") {
   if (is_clang && !is_nacl) {
     # TODO(thakis): Remove once silk/macros.h has been fixed
     cflags = [ "-Wno-expansion-to-defined" ]
   }
 }
 
-source_set("opus") {
+static_library("opus") {
   gypi_values = exec_script("//build/gypi_to_gn.py",
                             [ rebase_path("opus_srcs.gypi") ],
                             "scope",
                             [ "opus_srcs.gypi" ])
   sources = gypi_values.opus_common_sources
 
   defines = [
     "OPUS_BUILD",
     "OPUS_EXPORT=",
   ]
@@ skipping 213 matching lines @@
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     "//build/config/compiler:no_chromium_code",
     ":opus_test_config",
   ]
 
   deps = [
     ":opus",
   ]
 }