Platform validaor

[raju-opti]

Summary

• We have different entry points for different platforms. Also, we have platform specific code, entrypoints must not import code from unsupported platforms. This PR enforces this.

Test plan

Issues

[coveralls]

coverage: 78.003% (-0.4%) from 78.387%
when pulling 1a9203f on raju/platform_validator
into 860fca0 on master.