Revert "[toolchain] Disabling unused Mac toolchain downloads (#36760)" (#36958)

This reverts commit 31ac5c1ba8.

This change had been introduced under the impression we did not make use
of the hermetic toolchain to build the iOS code, but that's not
accurate. This is a partial revert of the change disabling the hermetic
SDK during the iOS checkout.

Bug: https://github.com/brave/brave-browser/issues/55812

DEPS

@@ -56,7 +56,7 @@ hooks = [
     # Download hermetic xcode for goma
     'name': 'download_hermetic_xcode',
     'pattern': '.',
-    'condition': 'checkout_mac',
+    'condition': 'checkout_mac or checkout_ios',
     'action': ['vpython3', 'build/mac/download_hermetic_xcode.py'],
   },
   {