Convert third_party source sets to static libraries.

third_party/boringssl/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/android/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build_overrides/build.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 import("BUILD.generated.gni")
 import("BUILD.generated_tests.gni")
@@ skipping 42 matching lines @@
 if (is_win && !is_msan) {
   import("//third_party/yasm/yasm_assemble.gni")
   yasm_assemble("boringssl_asm") {
     if (current_cpu == "x64") {
       sources = crypto_sources_win_x86_64
     } else if (current_cpu == "x86") {
       sources = crypto_sources_win_x86
     }
   }
 } else {
+  # This has no sources on some platforms so must be a source_set.
   source_set("boringssl_asm") {
     visibility = [ ":*" ]  # Only targets in this file can depend on this.
 
     defines = []
     sources = []
     asmflags = []
     include_dirs = [ "src/include" ]
 
     if ((current_cpu == "arm" || current_cpu == "arm64") && is_clang) {
       if (current_cpu == "arm") {
@@ skipping 130 matching lines @@
       } else if ("read_pem" == fuzzer) {
         libfuzzer_options = [ "max_len=512" ]
       } else if ("server" == fuzzer) {
         libfuzzer_options = [ "max_len=4096" ]
       } else if ("spki" == fuzzer) {
         libfuzzer_options = [ "max_len=1024" ]
       }
     }
   }
 }