Function to update the PATH to point to the "correct" brew installation depending on architecture

switch_brew.sh

# This function is for use on Macs with multiple brew installations (usually M1/arm64) Macs. This
# function will attempt to set your brew PATH to point to the correct brew based on the system arch.
#
# Usage:
#   # will automatically set brew based on architecture
#   $ switch_brew
#
#   # will set brew for arm64
#   $ switch_brew arm64
#
#   # will set brew for x86_64
#   $ switch_brew x86_64
function switch_brew {
  armBrewPath="/opt/homebrew/bin"
  switch_to=${1:-"$(uname -m)"}

  if [ "${switch_to}" = "arm64" ]; then
    PATH="${armBrewPath}:$PATH"
  else
    PATH=${PATH/":$armBrewPath"/} # delete any instances in the middle or at the end
    PATH=${PATH/"$armBrewPath:"/} # delete any instances at the beginning
  fi
}

This function should be added to your ~/.bashrc or ~/.zshrc (depending on which shell you use).

See homebrew's installation instructions for more context, or this explanation.

Additionally, this blog post goes into more explanation on the multi-brew setup.