build: Fix Boost.Process detection on macOS arm64
build: Fix Boost.Process detection on macOS arm64

Could be tested as follows:
```
% brew install boost@1.76
% ./autogen.sh
% ./configure --with-boost='/opt/homebrew/opt/boost@1.76'
```

Github-Pull: bitcoin#24521
Rebased-From: 1d4157a

bitcoinknots/bitcoin,bitcoinknots/bitcoin,bitcoinknots/bitcoin,bitcoinknots/bitcoin,bitcoinknots/bitcoin