`validation_flush_tests/getcoinscachesizestate` fails on RISCV-64 on master:
```
Running 394 test cases...
test/validation_flush_tests.cpp(99): error: in "validation_flush_tests/getcoinscachesizestate": check chainstate.GetCoinsCacheSizeState(tx_pool, MAX_COINS_CACHE_BYTES, 0) == CoinsCacheSizeState::OK has failed [1 != 0]

*** 1 failure is detected in the test module "Bitcoin Core Test Suite"
```
Haven't investigated why, yet. Apart from the architecture it could also be some dependency version causing the problem (this is a fedora rawhide install with very new versions of everything including gcc and boost).

Edit: see below, this is likely due to a newer `libstdc++`
BOOST_CHECK(!IsStandardTx(CTransaction(t), reason));
    BOOST_CHECK_EQUAL(reason, "scriptpubkey");
    
    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3804678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38");
    BOOST_CHECK_EQUAL(MAX_OP_RETURN_RELAY, t.vout[0].scriptPubKey.size());
    BOOST_CHECK(IsStandardTx(CTransaction(t), reason));
    
    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3804678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef3800");
    BOOST_CHECK_EQUAL(MAX_OP_RETURN_RELAY + 1, t.vout[0].scriptPubKey.size());
    reason.clear();
    BOOST_CHECK(!IsStandardTx(CTransaction(t), reason));
    BOOST_CHECK_EQUAL(reason, "scriptpubkey");
    
    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("");
    BOOST_CHECK(IsStandardTx(CTransaction(t), reason));
    t.vout[0].scriptPubKey = CScript() << OP_RETURN << ParseHex("00") << ParseHex("01");
    BOOST_CHECK(IsStandardTx(CTransaction(t), reason));
    
    t.vout[0].scriptPubKey = CScript() << OP_RETURN << OP_RESERVED << -1 << 0 << ParseHex("01") << 2 << 3 << 4 << 5 << 6 << 7 << 8 << 9 << 10 << 11 << 12 << 13 << 14 << 15 << 16;
    BOOST_CHECK(IsStandardTx(CTransaction(t), reason));
    t.vout[0].scriptPubKey = CScript() << OP_RETURN << 0 << ParseHex("01") << 2 << ParseHex("ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff");
    BOOST_CHECK(IsStandardTx(CTransaction(t), reason));
    
    t.vout[0].scriptPubKey = CScript() << OP_RETURN << OP_RETURN;
    reason.clear();
    BOOST_CHECK(!IsStandardTx(CTransaction(t), reason));
    BOOST_CHECK_EQUAL(reason, "scriptpubkey");
    
    t.vout.resize(1);
    t.vout[0].scriptPubKey = CScript() << OP_RETURN;