Convert third_party source sets to static libraries.

third_party/mesa/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/ui.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 
 config("mesa_headers_config") {
   include_dirs = [ "src/include" ]
@@ skipping 755 matching lines @@
       "KEYWORD2=GLAPIENTRY",
     ]
   }
 }
 
 if (is_linux) {
   config("wayland_drm_protocol_config") {
     include_dirs = [ "$generated_src_dir/egl/wayland/wayland-drm" ]
   }
 
-  source_set("wayland_drm_protocol") {
+  static_library("wayland_drm_protocol") {
     sources = [
       "$generated_src_dir/egl/wayland/wayland-drm/wayland-drm-client-protocol.h",
       "$generated_src_dir/egl/wayland/wayland-drm/wayland-drm-protocol.c",
       "$generated_src_dir/egl/wayland/wayland-drm/wayland-drm-server-protocol.h",
     ]
 
     deps = [
       "//third_party/wayland:wayland_util",
     ]
 
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
 
     public_configs = [ ":wayland_drm_protocol_config" ]
   }
 }