[Trivial] Fix makefile targets to use PHONY

[yihuaf]

Not all makefile target in Youki is using .PHONY target. We don't use any file targets, so fixing it properly for all makefile.

On a different note, there has been a lot of popularity in using justfile as command runner to invoke different command, especially for Rust projects. Since we use Makefile only as a command runner, I want to bring justfile up to see if there is any interest. Note, Makefile is definitely good enough for us. The upside is that justfile is a little more ergonomic being used as a command runner. The downside is that we have to install justfile as part of the dependency, whereas Makefile is more readily available. Food for thought :)

Reference: https://github.com/casey/just

[codecov-commenter]

Codecov Report

Merging #1743 (8a8b8e3) into main (04de7bf) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1743   +/-   ##
=======================================
  Coverage   68.69%   68.69%           
=======================================
  Files         121      121           
  Lines       13314    13314           
=======================================
  Hits         9146     9146           
  Misses       4168     4168           

[utam0k]

I didn't know case/just. I'll check it. Thanks