Allow to disable intel brew on ARM Mac.

[leptonyu]

I want to suggest a new step

• Which tool is this about? Where is its repository?
  topgrade
• Which operating systems are supported by this tool?
  macOS
• What should Topgrade do to figure out if the tool needs to be invoked?
  N/A
• Which exact commands should Topgrade run?
  topgrade
• Does it have a --dry-run option? i.e., print what should be done and exit
  N/A
• Does it need the user to confirm the execution? And does it provide a --yes
  option to skip this step?
  N/A

I want to suggest some general feature

Topgrade should be able to disable intel brew independently.

[SteveLauC]

Related to #515