Never use the hermetic xcode toolchain for iOS recipes.

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

Index: scripts/slave/recipes/ios/try.expected/gyp_goma.json
diff --git a/scripts/slave/recipes/ios/try.expected/gyp_goma.json b/scripts/slave/recipes/ios/try.expected/gyp_goma.json
index 39319bc49a0e76173f851d509a21d372687201f2..f3f7e6be4729d45499b2aaeb01d434962cac89ac 100644
--- a/scripts/slave/recipes/ios/try.expected/gyp_goma.json
+++ b/scripts/slave/recipes/ios/try.expected/gyp_goma.json
@@ -301,7 +301,6 @@
     ],
     "cwd": "[BUILDER_CACHE]/ios_simulator/src",
     "env": {
-      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "generate_build_files (with patch)"
@@ -394,7 +393,6 @@
       "/path/to/tmp/json"
     ],
     "env": {
-      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "clang_revision",
@@ -447,7 +445,6 @@
     ],
     "cwd": "[BUILDER_CACHE]/ios_simulator/src/out/Debug-iphonesimulator",
     "env": {
-      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "compile",