[Tidy] Shift Command to its own lib directory

[coder137]

No description provided.

[codecov]

Codecov Report

Merging #97 (4503727) into main (305bb2b) will increase coverage by 0.65%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main      #97      +/-   ##
==========================================
+ Coverage   72.41%   73.06%   +0.65%     
==========================================
  Files          17       18       +1     
  Lines         580      594      +14     
  Branches      191      191              
==========================================
+ Hits          420      434      +14     
  Misses         19       19              
  Partials      141      141              

Impacted Files	Coverage Δ
buildcc/lib/command/include/command/command.h	100.00% <ø> (ø)
buildcc/lib/command/src/command.cpp	71.43% <ø> (ø)
buildcc/lib/target/include/target/target.h	80.95% <ø> (ø)
buildcc/lib/target/src/target/source.cpp	66.29% <0.00%> (-0.37%)	⬇️
buildcc/lib/env/src/env.cpp	100.00% <0.00%> (ø)

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