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.
{
    wchar_t** wargv = CommandLineToArgvW(GetCommandLineW(), &argc);
    std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t> utf8_cvt;
    argv = new char*[argc];
    args.resize(argc);
    for (int i = 0; i < argc; i++) {
        args[i] = utf8_cvt.to_bytes(wargv[i]);
        argv[i] = &*args[i].begin();
    }
    LocalFree(wargv);
}
WinCmdLineArgs::~WinCmdLineArgs()
{
    delete[] argv;
}
std::pair<int, char**> WinCmdLineArgs::get()
{
    return std::make_pair(argc, argv);
}
#endif
}