bug(developer): Keyboard regression tests do not pass as expected, with unexpected output showing

### Describe the bug


Run any test from this [set](https://github.com/keymanapp/keyboards/tree/master/release/k/khmer_angkor/extras/regression_tests) and you should see fail results.

A character seems to be mysteriously and automatically added to the beginning of the expected output while the xml file does not have it there at all.

### Reproduce the bug

_No response_

### Expected behavior

_No response_

### Related issues

_No response_

### Keyman apps

- [ ] Keyman for Android
- [ ] Keyman for iPhone and iPad
- [ ] Keyman for Linux
- [ ] Keyman for macOS
- [ ] Keyman for Windows
- [X] Keyman Developer
- [ ] KeymanWeb
- [ ] Other - give details at bottom of form

### Keyman version

16.0.143

### Operating system

Edition Windows 10 Pro Version 22H2 Installed on ‎10/‎7/‎2020 OS build 19045.4355 Experience Windows Feature Experience Pack 1000.19056.1000.0

### Device

VM

### Target application

Keyman Developer

### Browser

_No response_

### Keyboard name

_No response_

### Keyboard version

_No response_

### Language name

_No response_

### Additional context

_No response_