feat: Add support for build arguments to build command

[antoinegelloz]

It is now possible to pass build-time variables with the --build-arg option for the dib build command:

dib build \
    --build-arg FOO1="bar1" \
    --build-arg FOO2=$BAR2 \
    --build-arg FOO3=${BAR3}

Alternatively, build arguments can also be set in the .dib.yaml config file:

build_arg:
  - FOO1="bar1"
  - FOO2=$BAR
  - FOO3=${BAR}

[codecov-commenter]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (e9fb779) 65.55% compared to head (2dfa834) 66.43%.
Report is 3 commits behind head on main.

❗ Current head 2dfa834 differs from pull request most recent head 5852832. Consider uploading reports for the commit 5852832 to get more accurate results

Files	Patch %	Lines
pkg/dib/generate_dag.go	72.22%	2 Missing and 3 partials ⚠️
pkg/dib/build.go	71.42%	0 Missing and 2 partials ⚠️
pkg/docker/builder.go	83.33%	0 Missing and 1 partial ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #449      +/-   ##
==========================================
+ Coverage   65.55%   66.43%   +0.87%     
==========================================
  Files          33       33              
  Lines        1864     1889      +25     
==========================================
+ Hits         1222     1255      +33     
+ Misses        542      529      -13     
- Partials      100      105       +5     

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