feat: remove file if it exists before creating new one

[jahzielv]

Checklist for submitter

If some of the following don't apply, delete the relevant line.

• Changes file added for user-visible changes in changes/ or orbit/changes/.
  See Changes files for more information.
• Added/updated tests
• Manual QA for all new/changed functionality

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (5f313c8) 67.34% compared to head (a09b779) 67.35%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
orbit/pkg/packaging/linux_shared.go	0.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15186   +/-   ##
=======================================
  Coverage   67.34%   67.35%           
=======================================
  Files        1021     1021           
  Lines       88118    88121    +3     
  Branches     2297     2297           
=======================================
+ Hits        59347    59350    +3     
  Misses      24351    24351           
  Partials     4420     4420           

Flag	Coverage Δ
backend	68.68% <0.00%> (+<0.01%)	⬆️

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[jahzielv]

@lucasmrod @mostlikelee @getvictor I was thinking about automated testing approaches for this fix, but haven't settled on anything satisfactory. The current packaging tests are not extensive fwiw, so maybe we don't need a new test for this?
One thought I had was to use testcontainers to verify that the package can be installed, but I haven't been able to make an ubuntu container work locally with this method. If y'all have any ideas I'd appreciate them!

[lucasmrod]

#13260

[lucasmrod]

LGTM!

[lucasmrod]

@lucasmrod @mostlikelee @getvictor I was thinking about automated testing approaches for this fix, but haven't settled on anything satisfactory. The current packaging tests are not extensive fwiw, so maybe we don't need a new test for this? One thought I had was to use testcontainers to verify that the package can be installed, but I haven't been able to make an ubuntu container work locally with this method. If y'all have any ideas I'd appreciate them!

How about testing buildNFPM? (Run that two times, first time with larger enroll than second, then unpack the secondly generated .deb and check that the enroll secret file matches the expected.)

[lucasmrod]

• We might also need to test RPM packages (probably has the same issue?)
• Adding the unit test.