Never use the hermetic xcode toolchain for iOS recipes.

scripts/slave/recipes/webrtc/ios.expected/basic.json

Index: scripts/slave/recipes/webrtc/ios.expected/basic.json
diff --git a/scripts/slave/recipes/webrtc/ios.expected/basic.json b/scripts/slave/recipes/webrtc/ios.expected/basic.json
index 17f5dd68335d91e08a439ee81a880104e9fe3f6f..9cee572d36f6f28807dd43aecf28c380bf4045f9 100644
--- a/scripts/slave/recipes/webrtc/ios.expected/basic.json
+++ b/scripts/slave/recipes/webrtc/ios.expected/basic.json
@@ -250,7 +250,6 @@
     ],
     "cwd": "[BUILDER_CACHE]/ios_debug/src",
     "env": {
-      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "generate_build_files"
@@ -267,7 +266,6 @@
       "/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",
@@ -317,7 +315,6 @@
     ],
     "cwd": "[BUILDER_CACHE]/ios_debug/src/out/Debug-iphonesimulator",
     "env": {
-      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "compile",