Fixing MPK support for polyglot isolates.

Author: tzezula

truffle/mx.truffle/mx_truffle.py

@@ -1667,7 +1667,8 @@ def __init__(self, language_suite, language_id, isolate_deps, isolate_build_opti
         build_args = [
             '--features=com.oracle.svm.enterprise.truffle.PolyglotIsolateGuestFeature',
             '-H:APIFunctionPrefix=truffle_isolate_',
-            '-H:+CopyLanguageResources'
+            '-H:+CopyLanguageResources',
+            '-H:+ProtectionKeys'
         ] + isolate_build_options
         super().__init__(language_suite, f'{language_id}.isolate', isolate_deps, ['Truffle'], None, f'{language_id}vm', **{'build_args': build_args})