Download the hermetic xcode toolchain on all bots that target mac.

scripts/slave/recipes/chromium_trybot.expected/full_tryserver_blink_mac10_11_blink_rel.json

Index: scripts/slave/recipes/chromium_trybot.expected/full_tryserver_blink_mac10_11_blink_rel.json
diff --git a/scripts/slave/recipes/chromium_trybot.expected/full_tryserver_blink_mac10_11_blink_rel.json b/scripts/slave/recipes/chromium_trybot.expected/full_tryserver_blink_mac10_11_blink_rel.json
index 6a4751dc1e616a27e39b7bbddc902f13de5bc085..991beb7b39d65f51c20be3fc27f9c0667e4fabbf 100644
--- a/scripts/slave/recipes/chromium_trybot.expected/full_tryserver_blink_mac10_11_blink_rel.json
+++ b/scripts/slave/recipes/chromium_trybot.expected/full_tryserver_blink_mac10_11_blink_rel.json
@@ -206,6 +206,7 @@
     ],
     "cwd": "[BUILDER_CACHE]/mac_layout/src",
     "env": {
+      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
       "GYP_CHROMIUM_NO_ACTION": "1",
       "GYP_DEFINES": "clang=1 component=static_library dcheck_always_on=1 fastbuild=1 gomadir='[CACHE]/cipd/goma' target_arch=x64 test_isolation_mode=prepare use_goma=1",
@@ -347,6 +348,7 @@
     ],
     "cwd": "[BUILDER_CACHE]/mac_layout/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)"
@@ -363,6 +365,7 @@
       "/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",
@@ -413,6 +416,7 @@
       "blink_tests"
     ],
     "env": {
+      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "compile (with patch)",
@@ -465,6 +469,7 @@
     ],
     "cwd": "[BUILDER_CACHE]/mac_layout",
     "env": {
+      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "webkit_tests (with patch)",
@@ -492,6 +497,7 @@
     ],
     "cwd": "[BUILDER_CACHE]/mac_layout",
     "env": {
+      "FORCE_MAC_TOOLCHAIN": "1",
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "archive_webkit_tests_results",