Prevent self hosted jobs to run on forks.

[Ouss4]

Summary

Run jobs that require self hosted runners only on the main repository.
#5521 (comment)
adafruit#11

Impact

Forks only.

[CLAassistant]

)
All committers have signed the CLA.

[igrr]

Does this mean that we can't test external contributions on self-hosted runners at all?

[Ouss4]

We can as long as they open a pull request in this repo. In their forks, it won't work.

• Self-hosted runner of this PR: https://github.com/espressif/arduino-esp32/runs/4441950944?check_suite_focus=true
• A PR in my fork with self-hosted runner still enabled: https://github.com/Ouss4/arduino-esp32/runs/4437402472?check_suite_focus=true been trying to find a runner since yesterday. I've seen in the Adafruit one that the workflow failed after a day and few hours.
• And this is another PR in my fork with self-hosted runner skipped: https://github.com/Ouss4/arduino-esp32/runs/4437364409?check_suite_focus=true

[igrr]

Got it, thanks for explaining. LGTM then!