ios: fix path to the test app

scripts/slave/recipes/ios/try.expected/swarming.json

 [
   {
     "cmd": [
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/ios/host_info.py",
       "--json-file",
       "/path/to/tmp/json"
     ],
     "name": "host and tools info",
     "~followup_annotations": [
       "@@@STEP_TEXT@<br />OS X 1.2.3, Xcode 6.7.8 (5D342509a)@@@",
@@ skipping 465 matching lines @@
       "@@@STEP_LOG_LINE@template.isolate@  ]@@@",
       "@@@STEP_LOG_LINE@template.isolate@}@@@",
       "@@@STEP_LOG_END@template.isolate@@@"
     ]
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
-      "{\n  \"args\": [\n    \"--config-variable\", \n    \"OS\", \n    \"ios\", \n    \"--config-variable\", \n    \"app_path\", \n    \"src/out/Debug-iphonesimulator/fake test.app\", \n    \"--config-variable\", \n    \"xcode_version\", \n    \"fake xcode version\", \n    \"--isolate\", \n    \"[SLAVE_BUILD]/template.isolate\", \n    \"--isolated\", \n    \"[TMP_BASE]/isolate_tmp_1/0.isolated\", \n    \"--path-variable\", \n    \"app_path\", \n    \"src/out/Debug-iphonesimulator/fake test.app\", \n    \"--config-variable\", \n    \"platform\", \n    \"fake device\", \n    \"--config-variable\", \n    \"version\", \n    \"8.1\"\n  ], \n  \"dir\": \"[SLAVE_BUILD]\", \n  \"version\": 1\n}",
+      "{\n  \"args\": [\n    \"--config-variable\", \n    \"OS\", \n    \"ios\", \n    \"--config-variable\", \n    \"app_path\", \n    \"[BUILDER_CACHE]/ios_simulator_swarming/src/out/Debug-iphonesimulator/fake test.app\", \n    \"--config-variable\", \n    \"xcode_version\", \n    \"fake xcode version\", \n    \"--isolate\", \n    \"[SLAVE_BUILD]/template.isolate\", \n    \"--isolated\", \n    \"[TMP_BASE]/isolate_tmp_1/0.isolated\", \n    \"--path-variable\", \n    \"app_path\", \n    \"[BUILDER_CACHE]/ios_simulator_swarming/src/out/Debug-iphonesimulator/fake test.app\", \n    \"--config-variable\", \n    \"platform\", \n    \"fake device\", \n    \"--config-variable\", \n    \"version\", \n    \"8.1\"\n  ], \n  \"dir\": \"[SLAVE_BUILD]\", \n  \"version\": 1\n}",
       "[TMP_BASE]/isolate_tmp_1/0.isolate.gen.json"
     ],
     "name": "isolate.generate 0.isolate.gen.json",
     "~followup_annotations": [
       "@@@STEP_NEST_LEVEL@1@@@",
       "@@@STEP_TEXT@fake test (fake device iOS 8.1)@@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@{@@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@  \"args\": [@@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"--config-variable\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"OS\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"ios\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"--config-variable\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"app_path\", @@@",
-      "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"src/out/Debug-iphonesimulator/fake test.app\", @@@",
+      "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"[BUILDER_CACHE]/ios_simulator_swarming/src/out/Debug-iphonesimulator/fake test.app\", @@@",

[smut, 2016/08/10 23:53:39]

This is wrong. This command needs to use relative paths because the absolute
paths on the builder do not exist on Swarming.

       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"--config-variable\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"xcode_version\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"fake xcode version\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"--isolate\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"[SLAVE_BUILD]/template.isolate\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"--isolated\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"[TMP_BASE]/isolate_tmp_1/0.isolated\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"--path-variable\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"app_path\", @@@",
-      "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"src/out/Debug-iphonesimulator/fake test.app\", @@@",
+      "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"[BUILDER_CACHE]/ios_simulator_swarming/src/out/Debug-iphonesimulator/fake test.app\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"--config-variable\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"platform\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"fake device\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"--config-variable\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"version\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@    \"8.1\"@@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@  ], @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@  \"dir\": \"[SLAVE_BUILD]\", @@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@  \"version\": 1@@@",
       "@@@STEP_LOG_LINE@0.isolate.gen.json@}@@@",
@@ skipping 161 matching lines @@
       "@@@STEP_LOG_END@json.output@@@",
       "@@@STEP_LINK@shard #0@https://chromium-swarm.appspot.com/user/task/10000@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]