`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++`
#include <util/strencodings.h>
#include <map>
#include <string>
#include <boost/algorithm/string/classification.hpp>
#include <boost/algorithm/string/split.hpp>
#include <boost/test/unit_test.hpp>
#include <univalue.h>
typedef std::vector<unsigned char> valtype;
extern UniValue read_json(const std::string& jsondata);
static std::map<std::string, unsigned int> mapFlagNames = {
    {std::string("NONE"), (unsigned int)SCRIPT_VERIFY_NONE},
    {std::string("P2SH"), (unsigned int)SCRIPT_VERIFY_P2SH},
    {std::string("STRICTENC"), (unsigned int)SCRIPT_VERIFY_STRICTENC},
    {std::string("DERSIG"), (unsigned int)SCRIPT_VERIFY_DERSIG},
    {std::string("LOW_S"), (unsigned int)SCRIPT_VERIFY_LOW_S},
    {std::string("SIGPUSHONLY"), (unsigned int)SCRIPT_VERIFY_SIGPUSHONLY},
    {std::string("MINIMALDATA"), (unsigned int)SCRIPT_VERIFY_MINIMALDATA},
    {std::string("NULLDUMMY"), (unsigned int)SCRIPT_VERIFY_NULLDUMMY},
    {std::string("DISCOURAGE_UPGRADABLE_NOPS"), (unsigned int)SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS},
    {std::string("CLEANSTACK"), (unsigned int)SCRIPT_VERIFY_CLEANSTACK},
    {std::string("MINIMALIF"), (unsigned int)SCRIPT_VERIFY_MINIMALIF},
    {std::string("NULLFAIL"), (unsigned int)SCRIPT_VERIFY_NULLFAIL},
    {std::string("CHECKLOCKTIMEVERIFY"), (unsigned int)SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY},
    {std::string("CHECKSEQUENCEVERIFY"), (unsigned int)SCRIPT_VERIFY_CHECKSEQUENCEVERIFY},
    {std::string("WITNESS"), (unsigned int)SCRIPT_VERIFY_WITNESS},
    {std::string("DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM"), (unsigned int)SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_WITNESS_PROGRAM},
    {std::string("WITNESS_PUBKEYTYPE"), (unsigned int)SCRIPT_VERIFY_WITNESS_PUBKEYTYPE},
    {std::string("CONST_SCRIPTCODE"), (unsigned int)SCRIPT_VERIFY_CONST_SCRIPTCODE},
};
unsigned int ParseScriptFlags(std::string strFlags)