test: Add imports for util bpf_cflags

This is required for the next commit.

test/functional/interface_usdt_mempool.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-# Copyright (c) 2022 The Bitcoin Core developers
+# Copyright (c) 2022-present The Bitcoin Core developers
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
@@ -20,7 +20,10 @@ from test_framework.blocktools import COINBASE_MATURITY
 from test_framework.messages import COIN, DEFAULT_MEMPOOL_EXPIRY_HOURS
 from test_framework.p2p import P2PDataStore
 from test_framework.test_framework import BitcoinTestFramework
-from test_framework.util import assert_equal
+from test_framework.util import (
+    assert_equal,
+    bpf_cflags,
+)
 from test_framework.wallet import MiniWallet
 
 MEMPOOL_TRACEPOINTS_PROGRAM = """