fix: build.options now have the full path to used platforms

[cmaglie]

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• Tests for the changes have been added (for bug fixes / features)
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What kind of change does this PR introduce?

Previously, the path to the folder containing the platforms was used (for example, /home/cmaglie/.arduino15/packages instead of /home/cmaglie/.arduino15/packages/arduino/hardware/avr/1.8.6). This kept the build.options file unchanged even if a platform was updated, leading to a possible cache reuse even if a full rebuild is required.

What is the current behavior?

~/Arduino/Blink$ arduino-cli compile --build-path build
Lo sketch usa 1438 byte (4%) dello spazio disponibile per i programmi. Il massimo è 32256 byte.
Le variabili globali usano 184 byte (8%) di memoria dinamica, lasciando altri 1864 byte liberi per le variabili locali. Il massimo è 2048 byte.
~/Arduino/Blink$ cat build/build.options.json 
{
  "additionalFiles": "",
  "compiler.optimization_flags": "",
  "customBuildProperties": "",
  "fqbn": "arduino:avr:uno",
  "hardwareFolders": "/home/cmaglie/.arduino15/packages,/home/cmaglie/Workspace/sketchbook-cores-beta/hardware",
  "otherLibrariesFolders": "/home/cmaglie/Workspace/sketchbook-cores-beta/libraries",
  "sketchLocation": "/home/cmaglie/Arduino/Blink"
}

What is the new behavior?

~/Arduino/Blink$ arduino-cli compile --build-path build
Lo sketch usa 1438 byte (4%) dello spazio disponibile per i programmi. Il massimo è 32256 byte.
Le variabili globali usano 184 byte (8%) di memoria dinamica, lasciando altri 1864 byte liberi per le variabili locali. Il massimo è 2048 byte.
~/Arduino/Blink$ cat build/build.options.json 
{
  "additionalFiles": "",
  "compiler.optimization_flags": "",
  "customBuildProperties": "",
  "fqbn": "arduino:avr:uno",
  "hardwareFolders": "/home/cmaglie/.arduino15/packages/arduino/hardware/avr/1.8.6,/home/cmaglie/.arduino15/packages/arduino/hardware/avr/1.8.6",
  "otherLibrariesFolders": "/home/cmaglie/Workspace/sketchbook-cores-beta/libraries",
  "sketchLocation": "/home/cmaglie/Arduino/Blink"
}
~/Arduino/Blink$ 

Does this PR introduce a breaking change, and is titled accordingly?

Other information

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.34%. Comparing base (28dbc33) to head (1b373d3).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3042      +/-   ##
==========================================
- Coverage   69.37%   69.34%   -0.04%     
==========================================
  Files         241      241              
  Lines       18591    18590       -1     
==========================================
- Hits        12898    12891       -7     
- Misses       4496     4503       +7     
+ Partials     1197     1196       -1     

Flag	Coverage Δ
unit	69.34% <100.00%> (-0.04%)	⬇️

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