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.
}
                    LogPrintf("Included configuration file %s\n", conf_file_name);
                } else {
                    error = "Failed to include configuration file " + conf_file_name;
                    return false;
                }
            }
            
            conf_file_names.clear();
            add_includes(chain_id,  chain_includes);
            add_includes({},  default_includes);
            std::string chain_id_final = GetChainName();
            if (chain_id_final != chain_id) {
                
                add_includes(chain_id_final);
            }
            for (const std::string& conf_file_name : conf_file_names) {
                tfm::format(std::cerr, "warning: -includeconf cannot be used from included files; ignoring -includeconf=%s\n", conf_file_name);
            }
        }
    }
    
    gArgs.ClearPathCache();
    if (!CheckDataDirOption()) {
        error = strprintf("specified data directory \"%s\" does not exist.", GetArg("-datadir", ""));
        return false;
    }
    return true;
}
std::string ArgsManager::GetChainName() const