Support building libs and apps for iOS, watchOS, and tvOS with bitcode

build/config/ios/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/ios/ios_sdk.gni")
 import("//build/config/sysroot.gni")
 import("//build/toolchain/toolchain.gni")
 
+declare_args() {
+  # Enabling this option makes clang compile to an intermediate
+  # representation ("bitcode"), and not to native code. This is preferred
+  # when including WebRTC in the apps that will be sent to Apple's App Store
+  # and mandatory for the apps that run on watchOS or tvOS.
+  # The option only works when building with Xcode (use_xcode_clang = true).
+  # Mimicking how Xcode handles it, the production builds (is_debug = false)
+  # get real bitcode sections added, while the debug builds (is_debug = true)
+  # only get bitcode-section "markers" added in them.
+  # NOTE: This option is ignored when building versions for the iOS simulator,
+  # where a part of libvpx is compiled from the assembly code written using
+  # Intel assembly syntax; Yasm / Nasm do not support emitting bitcode parts.
+  # That is not a limitation for now as Xcode mandates the presence of bitcode
+  # only when building bitcode-enabled projects for real devices (ARM CPUs).
+  enable_ios_bitcode = false
+}
+
 # This is included by reference in the //build/config/compiler:runtime_library
 # config that is applied to all targets. It is here to separate out the logic
 # that is iOS-only. Please see that target for advice on what should go in
 # :runtime_library vs. :compiler.
 config("runtime_library") {
   common_flags = [
     "-isysroot",
     sysroot,
 
     "-stdlib=libc++",
   ]
 
   if (use_ios_simulator) {
     common_flags += [ "-mios-simulator-version-min=$ios_deployment_target" ]
   } else {
     common_flags += [ "-miphoneos-version-min=$ios_deployment_target" ]
   }
 
+  if (use_xcode_clang && enable_ios_bitcode && !use_ios_simulator) {
+    if (is_debug) {
+      common_flags += [ "-fembed-bitcode-marker" ]
+    } else {
+      common_flags += [ "-fembed-bitcode" ]
+    }
+  }
+
   asmflags = common_flags
   cflags = common_flags
   ldflags = common_flags
 
   # TODO(crbug.com/634373): Remove once Xcode's libc++ has LLVM r256325. Most
   # likely this means one Xcode 8 is released and required.
   if (use_xcode_clang && get_path_info(ios_sdk_version, "name") != "10") {
     common_cc_flags = [
       "-isystem",
       rebase_path("//third_party/llvm-build/Release+Asserts/include/c++/v1",
@@ skipping 20 matching lines @@
 
   libs = [
     "Foundation.framework",
     "XCTest.framework",
   ]
 }
 
 group("xctest") {
   public_configs = [ ":xctest_config" ]
 }