While testing 17270 I noticed that master (bdda137878904e9401a84e308ac74c93c2ef87c1) does not run on NetBSD. I assume this started after #17085 changed the fallback locale from `C` to `C.UTF-8`. There doesn't seem to be a `C.UTF-8` locale on NetBSD.

```bash
src/bitcoind
terminate called after throwing an instance of 'std::runtime_error'
  what():  locale::facet::_S_create_c_locale name not valid
Abort trap (core dumped)
```

`LC_ALL=C src/bitcoind` works, `LC_ALL=en_US.UTF-8 src/bitcoind` does not.

```bash
locale
LANG=""
LC_CTYPE="en_US.UTF-8"
LC_COLLATE="C"
LC_TIME="C"
LC_NUMERIC="C"
LC_MONETARY="C"
LC_MESSAGES="C"
LC_ALL=""
```
{
    LOCK(cs_args);
    m_cached_datadir_path = fs::path();
    m_cached_network_datadir_path = fs::path();
    m_cached_blocks_path = fs::path();
}
std::optional<const ArgsManager::Command> ArgsManager::GetCommand() const
{
    Command ret;
    LOCK(cs_args);
    auto it = m_command.begin();
    if (it == m_command.end()) {
        
        return std::nullopt;
    }
    if (!m_accept_any_command) {
        
        ret.command = *(it++);
    }
    while (it != m_command.end()) {
        
        ret.args.push_back(*(it++));
    }
    return ret;
}
std::vector<std::string> ArgsManager::GetArgs(const std::string& strArg) const