message: doc: install qt5 when building on macOS
  Brew has updated such that qt now refers to Qt 6.0.1. If builders
  install this, configure will not work pick up qt. For now, install
  qt@5 (5.15.2), until required build system and likely source changes
  are made.
diff: @@ -19,7 +19,7 @@ Then install [Homebrew](https://brew.sh).
  ## Dependencies
  ```shell
  -brew install automake libtool boost miniupnpc libnatpmp pkg-config python qt libevent qrencode
  +brew install automake libtool boost miniupnpc libnatpmp pkg-config python qt@5 libevent qrencode
  ```
  If you run into issues, check [Homebrew's troubleshooting page](https://docs.brew.sh/Troubleshooting).
  