[ios/rbe] Fix iOS buildwith Goma RBE

Some targets want to copy files from $ios_sdk_platform_abs_path.
Since those points to sub-directory of $root_build_dir when goma
RBE is enabled, this causes failure at "gn gen" time since there
are no target creating those files according to gn.

To fix this, add a new target that pretends to create those files.

Bug: 1061487, webrtc:11429
Change-Id: I9d2330c4c6e041e59f24c459e50fe787602abde6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2102544
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#750560}

build/config/ios/BUILD.gn

@@ -127,3 +127,31 @@ config("xctest_config") {
 group("xctest") {
   public_configs = [ ":xctest_config" ]
 }
+
+# When building with Goma RBE, $ios_sdk_platform_abs_path corresponds to a
+# symlink below $root_build_dir that points to the real SDK to use. Because
+# the files are below $root_build_dir, it is not possible to list them as a
+# target input without gn complaining (as it can't find a target creating
+# those files).
+#
+# The symlinks are created by //build/config/mac/sdk_info.py script invoked
+# via exec_script() from //build/config/{ios/ios_sdk.gni,mac/mac_sdk.gni}.
+# As the invocation is done by exec_script, there is no target that can list
+# those files as output.
+#
+# To workaround this, add a target that pretends to create those files
+# (but does nothing). See https://crbug.com/1061487 for why this is needed.
+if (ios_use_goma_rbe) {
+  _xctrunner_path =
+      "$ios_sdk_platform_abs_path/Developer/Library/Xcode/Agents/XCTRunner.app"
+
+  action("copy_xctrunner_app") {
+    testonly = true
+    script = "//build/noop.py"
+    outputs = [
+      "$_xctrunner_path/Info.plist",
+      "$_xctrunner_path/PkgInfo",
+      "$_xctrunner_path/XCTRunner",
+    ]
+  }
+}

build/config/ios/ios_sdk.gni

@@ -108,7 +108,7 @@ if (ios_sdk_path == "") {
   if (ios_use_goma_rbe) {
     ios_sdk_info_args += [
       "--create_symlink_at",
-      rebase_path("$root_build_dir/sdk/xcode_links", "//"),
+      "sdk/xcode_links",
     ]
   }
   script_name = "//build/config/mac/sdk_info.py"

build/config/ios/rules.gni

@@ -1904,6 +1904,10 @@ template("ios_xcuitest_test_runner_bundle") {
              "-f=xml1",
              "-o=" + rebase_path(_output_name, root_build_dir),
            ] + rebase_path(sources, root_build_dir)
+
+    if (ios_use_goma_rbe) {
+      deps = [ "//build/config/ios:copy_xctrunner_app" ]
+    }
   }
 
   ios_info_plist(_info_plist_target) {
@@ -1932,6 +1936,10 @@ template("ios_xcuitest_test_runner_bundle") {
     sources = [ "$_xctrunner_path/PkgInfo" ]
 
     outputs = [ "{{bundle_contents_dir}}/PkgInfo" ]
+
+    if (ios_use_goma_rbe) {
+      deps = [ "//build/config/ios:copy_xctrunner_app" ]
+    }
   }
 
   _xctest_bundle = invoker.xctest_bundle
@@ -1961,6 +1969,10 @@ template("ios_xcuitest_test_runner_bundle") {
       ":$_pkginfo_bundle",
       ":$_xctest_bundle",
     ]
+
+    if (ios_use_goma_rbe) {
+      deps = [ "//build/config/ios:copy_xctrunner_app" ]
+    }
   }
 }
 

build/noop.py

+# Copyright 2020 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.
+"""Script that does nothing successfully."""