feat(#32): Add a `clean` step to the Makefile

[ozyx]

Fixes #32

• Adds a clean step to the Makefile
• Run the clean step as the first step in make all to ensure reproducible builds

Plus...

• Refactor and modernize the Makefile
  • Add .PHONY, .ONESHELL, and other modern Makefile best-practices to increase robustness
  • Use the full path to the python3 executable
  • use /bin/bash as the shell
  • .ONESHELL - run all commands in a recipe in a single shell
  • .SHELLFLAGS
    • -e: Exit immediately if a command exits with non-zero exit code
    • -u: Treat unset variables as an error when substituting
    • -o pipefail: Return value of a pipeline is the status of the last command to exit with a non-zero status
  • Add print_message helper function to print colorized messages to the terminal
  • Dynamically calculate the width of the terminal in order to print better headers