Describe the bug:

See https://github.com/servo/servo/actions/runs/12303074454/job/34337398349?pr=34601
For some reason the mozjs build system can't find python / python3 on self hosted runners.

To Reproduce:

See #34601, which forces a build of mozjs from source by bumping the mozjs version, which means that there is no prebuilt mozjs artifact available.

Platform:
Windows self hosted CI runner