This is being emitted with [GCC 10.2.1](https://packages.debian.org/bullseye/g++-arm-linux-gnueabihf), in some CI jobs: i.e https://github.com/bitcoin/bitcoin/pull/25972/checks?check_run_id=12423693655, or https://github.com/bitcoin/bitcoin/pull/25972/checks?check_run_id=12423693651 (where we actually turn on all our warning flags with depends builds).
```bash
In file included from test/miniscript_tests.cpp:19:
./script/miniscript.h:1197:71: error: comparison of integers of different signs: 'typename iterator_traits<int *>::difference_type' (aka 'int') and 'const uint32_t' (aka 'const unsigned int') [-Werror,-Wsign-compare]
                    return std::count(subs.begin(), subs.end(), true) >= node.k;
                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^  ~~~~~~
test/miniscript_tests.cpp:346:34: note: in instantiation of function template specialization 'miniscript::Node<CPubKey>::IsSatisfiable<(lambda at test/miniscript_tests.cpp:346:48)>' requested here
        bool satisfiable = node->IsSatisfiable([](const Node&) { return true; });
                                 ^
1 error generated.
```

cc @darosior 
#ifndef BITCOIN_SCRIPT_MINISCRIPT_H
#define BITCOIN_SCRIPT_MINISCRIPT_H
#include <algorithm>
#include <functional>
#include <numeric>
#include <memory>
#include <optional>
#include <string>
#include <vector>
#include <assert.h>
#include <cstdlib>
#include <policy/policy.h>
#include <primitives/transaction.h>
#include <script/script.h>
#include <span.h>
#include <util/spanparsing.h>
#include <util/strencodings.h>
#include <util/string.h>
#include <util/vector.h>
namespace miniscript {
/** This type encapsulates the miniscript type system properties.
 *