[libcxx] Fix a typo in config.py

libcxx/utils/libcxx/test/config.py

def configure_executor(self):
         te = eval(exec_str)
         if te:
             self.lit_config.note("Using executor: %r" % exec_str)
             if self.lit_config.useValgrind:
                 # We have no way of knowing where in the chain the
                 # ValgrindExecutor is supposed to go. It is likely
                 # that the user wants it at the end, but we have no
                 # way of getting at that easily.
-                selt.lit_config.fatal("Cannot infer how to create a Valgrind "
+                self.lit_config.fatal("Cannot infer how to create a Valgrind "
                                       " executor.")
         else:
             te = LocalExecutor()
             if self.lit_config.useValgrind:
                 te = ValgrindExecutor(self.lit_config.valgrindArgs, te)
 
         te.target_info = self.target_info