`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++`
{
    
    
    
    
    
    
    
    UniValue tests = read_json(std::string(json_tests::tx_valid, json_tests::tx_valid + sizeof(json_tests::tx_valid)));
    ScriptError err;
    for (unsigned int idx = 0; idx < tests.size(); idx++) {
        UniValue test = tests[idx];
        std::string strTest = test.write();
        if (test[0].isArray())
        {
            if (test.size() != 3 || !test[1].isStr() || !test[2].isStr())
            {
                BOOST_ERROR("Bad test: " << strTest);