micro-ROS error creating firmware

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I've installed the micro-ROS setup tools on my Macbook (Mohave) and I'm trying to create the firmware. After running the following command:

ros2 run micro_ros_setup create_firmware_ws.sh freertos esp32

I get the following error:

executing command [brew install libxml2]
Error: homebrew-cask is a shallow clone. To `brew update` first run:
  git -C "/usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask" fetch --unshallow
Warning: libxml2 2.9.10_2 is already installed and up-to-date
To reinstall 2.9.10_2, run `brew reinstall libxml2`
command return code [brew install libxml2]: 0
executing command [brew install llvm]
Error: homebrew-cask is a shallow clone. To `brew update` first run:
  git -C "/usr/local/Homebrew/Library/Taps/homebrew/homebrew-cask" fetch --unshallow
Warning: llvm 11.0.0 is already installed and up-to-date
To reinstall 11.0.0, run `brew reinstall llvm`
command return code [brew install llvm]: 0
Warning: Calling `brew list` to only list formulae is deprecated! Use `brew list --formula` instead.
Warning: Calling `brew list` to only list formulae is deprecated! Use `brew list --formula` instead.
ERROR: the following rosdeps failed to install
  homebrew: Failed to detect successful installation of [libxml2]
  homebrew: Failed to detect successful installation of [llvm]

It appears that llvm and libxml2 is installed so why is homebrew not detecting it?