bug: `brew` not found / fails when script is run via `sudo`

[gvatsal60]

Describe the bug

When running the script using the recommended sudo elevation (e.g., curl ... | sudo bash), the script fails to detect or update Homebrew (brew).

This happens due to a dual conflict:

1. PATH Reset: sudo strips out the user's custom environment variables, meaning /home/linuxbrew/.linuxbrew/bin is missing from the root $PATH. This causes check_command brew to report that Homebrew is not installed.
2. Root Restrictions: Homebrew explicitly blocks or misbehaves when executed directly as the root user, which could corrupt file permissions in the user's home directory.

To Reproduce

Run the update script inside a modern Linux distribution (especially those using sudo-rs or strict secure_path defaults):

curl -fsSL "https://raw.githubusercontent.com/gvatsal60/Linux-All-In-One-Update-Script/HEAD/.update.sh" | sudo bash

Expected behavior

The script should be able to safely locate the Homebrew binary and drop privileges back down to the local user account (NON_ROOT_USER) to perform the brew update routines securely.

Proposed Solution / Code Fix

We can resolve this by updating check_command to explicitly look for the standard Linux Homebrew installation path, and updating update_brew to execute the commands via su - "${NON_ROOT_USER}".

1. Update check_command to handle brew paths under sudo:

check_command() {
    command_name="$1"

    # Explicit handling for brew when run under a stripped sudo PATH
    if [ "${command_name}" = "brew" ] && [ -x "/home/linuxbrew/.linuxbrew/bin/brew" ]; then
        return 0
    fi

    if ! command -v "${command_name}" >/dev/null 2>&1; then
        print_err "${command_name} is not installed."
        return 1
    fi

    return 0
}

2. Update update_brew to safely run as the non-root user:

update_brew() {
    println "Update Brew Formula's"

    if ! check_command brew; then
        return
    fi

    # Safely drop privileges back to the normal user to run brew commands
    if [ "\({NON_ROOT_USER}" != "nobody" ] && [ "\){NON_ROOT_USER}" != "root" ]; then
        su - "\${NON_ROOT_USER}" -c '
            eval "\$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)"
            brew update && brew upgrade && brew cleanup -s
            echo "\nBrew Diagnostics"
            brew doctor && brew missing
        '
    else
        # Fallback if no valid non-root user was resolved
        eval "\$(/home/linuxbrew/.linuxbrew/bin/brew shellenv)"
        brew update && brew upgrade && brew cleanup -s
        println "Brew Diagnostics"
        brew doctor && brew missing
    fi
}