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 
} else if (in[j] == 'u') {
                    script_size += 4;
                    to_parse.emplace_back(ParseContext::WRAP_U, -1, -1);
                } else if (in[j] == 't') {
                    script_size += 1;
                    to_parse.emplace_back(ParseContext::WRAP_T, -1, -1);
                } else if (in[j] == 'l') {
                    
                    script_size += 4;
                    constructed.push_back(MakeNodeRef<Key>(internal::NoDupCheck{}, Fragment::JUST_0));
                    to_parse.emplace_back(ParseContext::OR_I, -1, -1);
                } else {
                    return {};
                }
                last_was_v = (in[j] == 'v');
            }
            to_parse.emplace_back(ParseContext::EXPR, -1, -1);
            if (colon_index) in = in.subspan(*colon_index + 1);
            break;
        }
        case ParseContext::EXPR: {
            if (Const("0", in)) {
                constructed.push_back(MakeNodeRef<Key>(internal::NoDupCheck{}, Fragment::JUST_0));
            } else if (Const("1", in)) {
                constructed.push_back(MakeNodeRef<Key>(internal::NoDupCheck{}, Fragment::JUST_1));
            } else if (Const("pk(", in)) {
                auto res = ParseKeyEnd<Key, Ctx>(in, ctx);
                if (!res) return {};
                auto& [key, key_size] = *res;
                constructed.push_back(MakeNodeRef<Key>(internal::NoDupCheck{}, Fragment::WRAP_C, Vector(MakeNodeRef<Key>(internal::NoDupCheck{}, Fragment::PK_K, Vector(std::move(key))))));