Test on macOS 12.2.1 against the master branch. #24397 doesn't fix it.

```
brew info boost
boost: stable 1.78.0 (bottled), HEAD
...
./configure --enable-external-signer
...
checking for boostlib >= 1.64.0 (106400)... yes
checking whether Boost.Process can be used... no
configure: error: External signing is not supported for this Boost version
```

It does work with boost 1.76 (there was no 1.77 release in home-brew):

```
brew install boost@1.76
...
LDFLAGS="-L/usr/local/opt/boost@1.76/lib" CPPFLAGS="-I/usr/local/opt/boost@1.76/include" ./configure --enable-external-signer
...
checking for boostlib >= 1.64.0 (106400)... yes
checking whether Boost.Process can be used... yes
...
Options used to compile and link:
  external signer = yes
```

There's nothing in the release notes about Boost.Process for either [1.77](https://www.boost.org/users/history/version_1_77_0.html) or [1.78](https://www.boost.org/users/history/version_1_78_0.html).

The Homebrew [formula changes](https://github.com/Homebrew/homebrew-core/commits/master/Formula/boost.rb) are nothing but a trivial version and hash bump.
unsigned int flags, std::string& error)
{
    
    if (key.negated) {
        if (flags & ArgsManager::DISALLOW_NEGATION) {
            error = strprintf("Negating of -%s is meaningless and therefore forbidden", key.name);
            return std::nullopt;
        }
        
        if (!InterpretBool(value)) {
            LogPrintf("Warning: parsed potentially confusing double-negative -%s=%s\n", key.name, value);
            return true;
        }
        return false;
    }
    return value;
}
ArgsManager::ArgsManager() {}
ArgsManager::~ArgsManager() {}