Fixed compile regression

[cmaglie]

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• The PR has no duplicates (please search among the Pull Requests
  before creating one)
• The PR follows
  our contributing guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)
• UPGRADING.md has been updated with a migration guide (for breaking changes)

• What kind of change does this PR introduce?
  Fix a weird compile regression.

• What is the current behavior?
  The runtime.tools.PACKAGER-TOOL-VERSION.* variables are not populated (unless they are specified as a platform dependcy in the package_xxx_index.json and that index file is present).

• What is the new behavior?
  The above bug is fixed.

• Does this PR introduce a breaking change, and is titled accordingly?
  No

[codecov]

Codecov Report

Merging #1867 (ca7730f) into master (14c8500) will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1867      +/-   ##
==========================================
+ Coverage   36.62%   36.67%   +0.04%     
==========================================
  Files         231      231              
  Lines       19610    19609       -1     
==========================================
+ Hits         7182     7191       +9     
+ Misses      11600    11593       -7     
+ Partials      828      825       -3     

Flag	Coverage Δ
unit	36.67% <100.00%> (+0.04%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
legacy/builder/hardware_loader.go	88.88% <100.00%> (-0.40%)	⬇️
arduino/cores/packagemanager/package_manager.go	66.58% <0.00%> (+0.75%)	⬆️
arduino/cores/packagemanager/loader.go	74.30% <0.00%> (+1.13%)	⬆️

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