[mobile] add buck build for mobile targets (#76480)
Create buck targets to replicate internal BUCK build, including
- XNNPACK
- QNNPACK
- C10
- aten_cpu
- torch_mobile_core
- torch_mobile_all_ops
- ptmobile_benchmark
And able to run mobilenet v2 using ptmobile_benchmark (with all ops).
Pull Request resolved: https://github.com/pytorch/pytorch/pull/76480
Approved by: https://github.com/seemethere, https://github.com/dreiss
