setup the correct version of Xcode

scripts/slave/recipes/flutter/flutter.expected/enumerate_xcode_installations.json

 [
   {
     "cmd": [
       "python",
       "-u",
-      "\nimport os, sys\nfrom common import chromium_utils # Error? See https://crbug.com/584783.\n\npath = sys.argv[1]\nif os.path.exists(path):\n  for p in (os.path.join(path, x) for x in os.listdir(path)):\n    if os.path.isdir(p):\n      chromium_utils.RemoveDirectory(p)\n    else:\n      os.unlink(p)\n",
-      "[SLAVE_BUILD]"
-    ],
-    "cwd": "[SLAVE_BUILD]",
-    "name": "rmcontents everything",
-    "~followup_annotations": [
-      "@@@STEP_LOG_LINE@python.inline@@@@",
-      "@@@STEP_LOG_LINE@python.inline@import os, sys@@@",
-      "@@@STEP_LOG_LINE@python.inline@from common import chromium_utils # Error? See https://crbug.com/584783.@@@",
-      "@@@STEP_LOG_LINE@python.inline@@@@",
-      "@@@STEP_LOG_LINE@python.inline@path = sys.argv[1]@@@",
-      "@@@STEP_LOG_LINE@python.inline@if os.path.exists(path):@@@",
-      "@@@STEP_LOG_LINE@python.inline@  for p in (os.path.join(path, x) for x in os.listdir(path)):@@@",
-      "@@@STEP_LOG_LINE@python.inline@    if os.path.isdir(p):@@@",
-      "@@@STEP_LOG_LINE@python.inline@      chromium_utils.RemoveDirectory(p)@@@",
-      "@@@STEP_LOG_LINE@python.inline@    else:@@@",
-      "@@@STEP_LOG_LINE@python.inline@      os.unlink(p)@@@",
-      "@@@STEP_LOG_END@python.inline@@@"
-    ]
-  },
-  {
-    "cmd": [
-      "python",
-      "-u",
       "RECIPE_MODULE[depot_tools::git]/resources/git_setup.py",
       "--path",
       "[SLAVE_BUILD]/flutter",
       "--url",
       "https://chromium.googlesource.com/external/github.com/flutter/flutter"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "git setup"
   },
   {
@@ skipping 58 matching lines @@
       "submodule",
       "update",
       "--init",
       "--recursive"
     ],
     "cwd": "[SLAVE_BUILD]/flutter",
     "name": "submodule update"
   },
   {
     "cmd": [
-      "[SLAVE_BUILD]/flutter/infra/download_android_tools.py"
+      "python",
+      "-u",
+      "[BUILD]/scripts/slave/ios/find_xcode.py",
+      "--json-file",
+      "/path/to/tmp/json"
     ],
     "cwd": "[SLAVE_BUILD]",
-    "name": "download android tools"
+    "env": {
+      "ANDROID_HOME": "[SLAVE_BUILD]/flutter/infra/android_tools",
+      "PATH": "[SLAVE_BUILD]/flutter/bin:[SLAVE_BUILD]/flutter/bin/cache/dart-sdk/bin:%(PATH)s",
+      "PUB_CACHE": "[SLAVE_BUILD]/.pub-cache"
+    },
+    "name": "enumerate_xcode_installations",
+    "~followup_annotations": [
+      "@@@STEP_LOG_LINE@json.output@{@@@",
+      "@@@STEP_LOG_LINE@json.output@  \"some\": \"json\"@@@",
+      "@@@STEP_LOG_LINE@json.output@}@@@",
+      "@@@STEP_LOG_END@json.output@@@"
+    ]
   },
   {
     "cmd": [
       "flutter",
       "doctor"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "ANDROID_HOME": "[SLAVE_BUILD]/flutter/infra/android_tools",
       "PATH": "[SLAVE_BUILD]/flutter/bin:[SLAVE_BUILD]/flutter/bin/cache/dart-sdk/bin:%(PATH)s",
@@ skipping 273 matching lines @@
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
       "[DEPOT_TOOLS]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "[SLAVE_BUILD]/flutter/packages/flutter/doc/api",
-      "gs://docs.flutter.io/flutter"
+      "gs://docs.flutter.io/packages/flutter"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "ANDROID_HOME": "[SLAVE_BUILD]/flutter/infra/android_tools",
       "PATH": "[SLAVE_BUILD]/flutter/bin:[SLAVE_BUILD]/flutter/bin/cache/dart-sdk/bin:%(PATH)s",
       "PUB_CACHE": "[SLAVE_BUILD]/.pub-cache"
     },
     "name": "gsutil rsync flutter/doc/api"
   },
   {
@@ skipping 16 matching lines @@
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
       "[DEPOT_TOOLS]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "[SLAVE_BUILD]/flutter/packages/playfair/doc/api",
-      "gs://docs.flutter.io/playfair"
+      "gs://docs.flutter.io/packages/playfair"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "ANDROID_HOME": "[SLAVE_BUILD]/flutter/infra/android_tools",
       "PATH": "[SLAVE_BUILD]/flutter/bin:[SLAVE_BUILD]/flutter/bin/cache/dart-sdk/bin:%(PATH)s",
       "PUB_CACHE": "[SLAVE_BUILD]/.pub-cache"
     },
     "name": "gsutil rsync playfair/doc/api"
   },
   {
@@ skipping 16 matching lines @@
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
       "[DEPOT_TOOLS]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "[SLAVE_BUILD]/flutter/packages/cassowary/doc/api",
-      "gs://docs.flutter.io/cassowary"
+      "gs://docs.flutter.io/packages/cassowary"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "ANDROID_HOME": "[SLAVE_BUILD]/flutter/infra/android_tools",
       "PATH": "[SLAVE_BUILD]/flutter/bin:[SLAVE_BUILD]/flutter/bin/cache/dart-sdk/bin:%(PATH)s",
       "PUB_CACHE": "[SLAVE_BUILD]/.pub-cache"
     },
     "name": "gsutil rsync cassowary/doc/api"
   },
   {
@@ skipping 16 matching lines @@
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
       "[DEPOT_TOOLS]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "[SLAVE_BUILD]/flutter/packages/flutter_test/doc/api",
-      "gs://docs.flutter.io/flutter_test"
+      "gs://docs.flutter.io/packages/flutter_test"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "ANDROID_HOME": "[SLAVE_BUILD]/flutter/infra/android_tools",
       "PATH": "[SLAVE_BUILD]/flutter/bin:[SLAVE_BUILD]/flutter/bin/cache/dart-sdk/bin:%(PATH)s",
       "PUB_CACHE": "[SLAVE_BUILD]/.pub-cache"
     },
     "name": "gsutil rsync flutter_test/doc/api"
   },
   {
@@ skipping 16 matching lines @@
       "-u",
       "RECIPE_MODULE[build::gsutil]/resources/gsutil_wrapper.py",
       "--",
       "[DEPOT_TOOLS]/gsutil.py",
       "----",
       "-m",
       "rsync",
       "-d",
       "-r",
       "[SLAVE_BUILD]/flutter/packages/flutter_sprites/doc/api",
-      "gs://docs.flutter.io/flutter_sprites"
+      "gs://docs.flutter.io/packages/flutter_sprites"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "ANDROID_HOME": "[SLAVE_BUILD]/flutter/infra/android_tools",
       "PATH": "[SLAVE_BUILD]/flutter/bin:[SLAVE_BUILD]/flutter/bin/cache/dart-sdk/bin:%(PATH)s",
       "PUB_CACHE": "[SLAVE_BUILD]/.pub-cache"
     },
     "name": "gsutil rsync flutter_sprites/doc/api"
   },
   {
@@ skipping 43 matching lines @@
       "@@@STEP_LOG_LINE@python.inline@  chromium_utils.RemoveDirectory(sys.argv[1])@@@",
       "@@@STEP_LOG_END@python.inline@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]