Increase the default stack size when using the library launcher

Author: timfel

mx.graalpython/mx_graalpython.py

@@ -2052,6 +2052,9 @@ def verify_ci(dest_suite, common_ci_dir="ci_common", args=None, ext=('.jsonnet',
                 '-Dpolyglot.python.PosixModuleBackend=native'
             ],
             language='python',
+            default_vm_args=[
+                '--vm.Xss16777216', # request 16M of stack
+            ],
         )
     ],
     priority=5,