better handling of path differences for MSI installers

[roperzh]

Related to #7036, Tested in:

• macOS via fleetctl package --type=msi (non-native)
• Linux native via docker run -v "$(pwd)" fleetdm/fleetctl package --type=msi (native)
• Windows via fleetctl pacakge --type=msi (thanks to @edwardsb) (non-native)

Checklist for submitter

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

• Changes file added for user-visible changes (in changes/ and/or orbit/changes/).
• Added/updated tests
• Manual QA for all new/changed functionality

[codecov-commenter]

Codecov Report

Merging #7035 (efb0c1d) into main (82ba1a0) will increase coverage by 0.25%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #7035      +/-   ##
==========================================
+ Coverage   59.72%   59.97%   +0.25%     
==========================================
  Files         405      403       -2     
  Lines       37877    37712     -165     
==========================================
- Hits        22622    22619       -3     
+ Misses      13038    12876     -162     
  Partials     2217     2217              

Impacted Files	Coverage Δ
orbit/pkg/packaging/wix/wix.go
orbit/pkg/packaging/wix/transform.go

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[roperzh]

this was the crux of the problem, as we were providing Windows-like paths on Windows for the bind mount

[lucasmrod]

Looks great!

Were you able to test both modes? (native and !native)

[roperzh]

Were you able to test both modes? (native and !native)

yes! I updated the list in the PR description to include (native) or (non-native) to the list of targets we tested so it's more clear. The list is:

• macOS via fleetctl package --type=msi (non-native)
• Linux native via docker run -v "$(pwd)" fleetdm/fleetctl package --type=msi (native)
• Windows via fleetctl pacakge --type=msi (thanks to @\edwardsb) (non-native)