The `make install` script, which most users would run via `sudo` to install into `/usr/local`, will use the current umask of the root user when creating certain files and directories. If one uses a restrictive umask by default (e.g. `umask 077`), this means that only the root user will be able to use the full Bitcoin package.

**Expected behavior**

The install script creates all directories and files, including man pages, etc., with permissions `644` / `755`.

**Actual behavior**

Certain folders are created using the default umask, e.g.:

- /usr/local/share/man/man1/
- /usr/local/lib/pkgconfig/
- [...]

This means that only root can access files in these folders and other users won't be able to read the man pages (for example).

**To reproduce**

```bash
$ ./autogen.sh
$ make
$ sudo -iu root
% umask 077
% make install
```

**System information**

OS: Linux
bitcoind version: HEAD
{
    Assert(cmd.find('=') == std::string::npos);
    Assert(cmd.at(0) != '-');
    LOCK(cs_args);
    m_accept_any_command = false; 
    std::map<std::string, Arg>& arg_map = m_available_args[OptionsCategory::COMMANDS];
    auto ret = arg_map.emplace(cmd, Arg{"", help, ArgsManager::COMMAND});
    Assert(ret.second); 
}
void ArgsManager::AddArg(const std::string& name, const std::string& help, unsigned int flags, const OptionsCategory& cat)
{
    Assert((flags & ArgsManager::COMMAND) == 0); 
    
    size_t eq_index = name.find('=');
    if (eq_index == std::string::npos) {
        eq_index = name.size();
    }
    std::string arg_name = name.substr(0, eq_index);
    LOCK(cs_args);
    std::map<std::string, Arg>& arg_map = m_available_args[cat];
    auto ret = arg_map.emplace(arg_name, Arg{name.substr(eq_index, name.size() - eq_index), help, flags});
    assert(ret.second); 
    if (flags & ArgsManager::NETWORK_ONLY) {
        m_network_only_args.emplace(arg_name);
    }
}
void ArgsManager::AddHiddenArgs(const std::vector<std::string>& names)