Prepare the code to run ios tests with the standalone recipe.

The flags isolated-script-test-output and isolated-script-test-perf-output need to be consumed by the tests.

The generated .app folder in added in the data list of the gni file.
This will make it available in the runtime_deps file and thus will be populated to the swarming tasks.

Bug: webrtc:13556
Change-Id: I2c75774b847d9f686c3abc00ba0400bbc3fcefae
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/240520
Reviewed-by: Artem Titov <titovartem@webrtc.org>
Reviewed-by: Christoffer Jansson <jansson@google.com>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Jeremy Leconte <jleconte@google.com>
Cr-Commit-Position: refs/heads/main@{#36029}

test/test_main_lib.cc

@@ -57,7 +57,7 @@ ABSL_FLAG(
     "described by histogram.proto in "
     "https://chromium.googlesource.com/catapult/.");
 
-#else
+#endif
 
 ABSL_FLAG(std::string,
           isolated_script_test_output,
@@ -72,8 +72,6 @@ ABSL_FLAG(
     "described by histogram.proto in "
     "https://chromium.googlesource.com/catapult/.");
 
-#endif
-
 constexpr char kPlotAllMetrics[] = "all";
 ABSL_FLAG(std::vector<std::string>,
           plot,