fix Ctrl-C / SIGINT behaviour for pyinstaller-made binaries, fixes #8155

[ThomasWaldmann]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 20.00000% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 82.48%. Comparing base (736ffbd) to head (dfb8d20).
Report is 20 commits behind head on 1.4-maint.

Files	Patch %	Lines
src/borg/helpers/process.py	20.00%	8 Missing ⚠️

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Additional details and impacted files

@@              Coverage Diff              @@
##           1.4-maint    #8167      +/-   ##
=============================================
+ Coverage      82.15%   82.48%   +0.32%     
=============================================
  Files             38       38              
  Lines          11012    11019       +7     
  Branches        2112     2114       +2     
=============================================
+ Hits            9047     9089      +42     
+ Misses          1389     1362      -27     
+ Partials         576      568       -8     

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