add mobile build CI with host toolchain (#30292)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/30292
We already have CI jobs to build Android/iOS libraries, but there are
two issues:
- It's no easy for people who are not regularly working on mobile to debug
these CI errors as they need setup Android/iOS build environment;
- It's hard to run cross-compiled mobile libraries as it requires
emulator. It happened a couple times recently that it can build but fail
to load and run a model with mobile build.
To address these problems, create this new CI job to build mobile
library with linux host toolchain so that we can build & test without
involving Android/iOS environment/simulator. Will add tests on top of it next.
Test Plan: - check the new CI job
Differential Revision: D18654074
Pulled By: ljk53
fbshipit-source-id: eb1baee97a7b52c44979dbf1719c3357e08f895e
