iOS: Use JSON for GN configuration instead of MB + remove symbols

tools-webrtc/ios/tryserver.webrtc/ios32_sim_ios9_dbg.json

Index: tools-webrtc/ios/tryserver.webrtc/ios32_sim_ios9_dbg.json
diff --git a/tools-webrtc/ios/tryserver.webrtc/ios32_sim_ios9_dbg.json b/tools-webrtc/ios/tryserver.webrtc/ios32_sim_ios9_dbg.json
index 96c4964973b8571258a1a20dcc78f971a4598696..6c4d6980359f84bd71e0d0ae59fea097d1b67507 100644
--- a/tools-webrtc/ios/tryserver.webrtc/ios32_sim_ios9_dbg.json
+++ b/tools-webrtc/ios/tryserver.webrtc/ios32_sim_ios9_dbg.json
@@ -1,14 +1,14 @@
 {
   "comments": [
-    "Tests for 32-bit iOS simulators.",
-    "gn_args in this file is only read by the buildbot recipe; ",
-    "webrtc/build/mb_config.pyl contains the actual build configuration.",
-    "TODO(kjellander): remove gn_args when the recipe is updated."
+    "Tests for 32-bit iOS simulators."
   ],
   "xcode version": "8.0",
   "gn_args": [
+    "goma_dir=\"$(goma_dir)\"",
+    "is_component_build=false",
     "is_debug=true",
     "target_cpu=\"x86\"",
+    "target_os=\"ios\"",
     "use_goma=true"
   ],
   "use_analyze": false,