Change the x86{,_64} intrinsic targets in //third_party/libvpx to be source_sets.

third_party/libvpx/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("//build/config/android/config.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//third_party/libvpx/libvpx_srcs.gni")
 import("//third_party/yasm/yasm_assemble.gni")
 
@@ skipping 96 matching lines @@
     include_dirs = [
       platform_include_dir,
       "//third_party/libvpx/source/config",
       "//third_party/libvpx/source/libvpx",
       target_gen_dir,
     ]
   }
 }
 
 if (current_cpu == "x86" || current_cpu == "x64") {
-  static_library("libvpx_intrinsics_mmx") {
+  # The following targets are deliberately source_set rather than
+  # static_library. The :libvpx target exposes these intrinsic implementations
+  # via global function pointer symbols, which hides the object dependency at
+  # link time. On Mac, this results in undefined references to the intrinsic
+  # symbols.
+
+  source_set("libvpx_intrinsics_mmx") {
     configs += [ ":libvpx_config" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     configs += [ ":libvpx_warnings" ]
     if (!is_win) {
       cflags = [ "-mmmx" ]
     }
     if (current_cpu == "x86") {
       sources = libvpx_srcs_x86_mmx
     } else if (current_cpu == "x64") {
       sources = libvpx_srcs_x86_64_mmx
     }
   }
 
-  static_library("libvpx_intrinsics_sse2") {
+  source_set("libvpx_intrinsics_sse2") {
     configs += [ ":libvpx_config" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     configs += [ ":libvpx_warnings" ]
     if (!is_win || is_clang) {
       cflags = [ "-msse2" ]
     }
     if (current_cpu == "x86") {
       sources = libvpx_srcs_x86_sse2
     } else if (current_cpu == "x64") {
       sources = libvpx_srcs_x86_64_sse2
     }
   }
 
-  static_library("libvpx_intrinsics_ssse3") {
+  source_set("libvpx_intrinsics_ssse3") {
     configs += [ ":libvpx_config" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     configs += [ ":libvpx_warnings" ]
     if (!is_win || is_clang) {
       cflags = [ "-mssse3" ]
     }
     if (current_cpu == "x86") {
       sources = libvpx_srcs_x86_ssse3
     } else if (current_cpu == "x64") {
       sources = libvpx_srcs_x86_64_ssse3
     }
   }
 
-  static_library("libvpx_intrinsics_sse4_1") {
+  source_set("libvpx_intrinsics_sse4_1") {
     configs += [ ":libvpx_config" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     configs += [ ":libvpx_warnings" ]
     if (!is_win || is_clang) {
       cflags = [ "-msse4.1" ]
     }
     if (current_cpu == "x86") {
       sources = libvpx_srcs_x86_sse4_1
     } else if (current_cpu == "x64") {
       sources = libvpx_srcs_x86_64_sse4_1
     }
   }
 
-  static_library("libvpx_intrinsics_avx") {
+  source_set("libvpx_intrinsics_avx") {
     configs += [ ":libvpx_config" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     configs += [ ":libvpx_warnings" ]
     if (is_win) {
       cflags = [ "/arch:AVX" ]
     } else {
       cflags = [ "-mavx" ]
     }
     if (current_cpu == "x86") {
       sources = libvpx_srcs_x86_avx
     } else if (current_cpu == "x64") {
       sources = libvpx_srcs_x86_64_avx
     }
   }
 
-  static_library("libvpx_intrinsics_avx2") {
+  source_set("libvpx_intrinsics_avx2") {
     configs += [ ":libvpx_config" ]
     configs -= [ "//build/config/compiler:chromium_code" ]
     configs += [ "//build/config/compiler:no_chromium_code" ]
     configs += [ ":libvpx_warnings" ]
     if (is_win) {
       cflags = [ "/arch:AVX2" ]
     } else {
       cflags = [ "-mavx2" ]
     }
     if (current_cpu == "x86") {
@@ skipping 104 matching lines @@
   }
   if (is_android) {
     deps += [ "//third_party/android_tools:cpu_features" ]
   }
   if (current_cpu == "arm") {
     deps += [ ":libvpx_assembly_arm" ]
   }
 
   public_configs = [ ":libvpx_external_config" ]
 }