Describe the problem

Around early June, the arduino/compile-sketches-action (https://github.com/arduino/compile-sketches/) fails for the Teensy core (https://www.pjrc.com/teensy/package_teensy_index.json). The error message is:

The compilation itself seems to work, as before, but always ends with:

Opening Teensy Loader...
Unable find Teensy Loader. (p) Is the Teensy Loader application running?
quit

Both the above message, and the unsuccessful exit are new.

Testing the various components involved, this is neither due to updates in compile-sketches, nor it the core. However, downgrading arduino-cli to v0.35.3 fixes the issue.

It should be noted that an upload is absolutely not required at this point. We're essentially just running arduino-cli compile, here.

Further resources:

• Example of a successful run in the Mozzi library (June 9th): https://github.com/sensorium/Mozzi/actions/runs/9438094175/job/259947127
• Example of a failed run in the Mozzi library (June 12th): https://github.com/sensorium/Mozzi/actions/runs/9488741406/job/26270443137
• Discussion on the Teensy forum: https://forum.pjrc.com/index.php?threads/teensy-boards-starting-to-fail-in-github-actions-arduino-compile-sketches.75247/

To reproduce

This probably needs to be run inside a github-action, where the Teensy loader is not available.

An example workflow shall contain:

steps:
 - name: Checkout repository
 uses: actions/checkout@v4
 - name: Compile examples
 uses: arduino/compile-sketches@v1
 with:
 cli-version: 0.35.3 # may or may not be given, to toggle triggering the bug
 github-token: ${{ secrets.GITHUB_TOKEN }}
 fqbn: teensy:avr:teensy36
 platforms: |
 - name: teensy:avr
 source-url: https://www.pjrc.com/teensy/package_teensy_index.json
 sketch-paths: |
 - examples

Expected behavior

arduino-cli compile should compile, only, not attempt to contact the upload daemon.

Arduino CLI version

v1.0.x

Operating system

Linux

Operating system version

Ubuntu (via github actions docker)

Additional context

No response

Issue checklist

• I searched for previous reports in the issue tracker
• I verified the problem still occurs when using the nightly build
• My report contains all necessary details