[native] Add yarn clean-commoncpp to package.json

Summary: Ran into some linker errors during Android build due to leftover build artifacts. Was able to fix things up by deleting these build folders.

Test Plan: Built stuff, ran command, watched the build folders disappear.

Reviewers: tomek, varun, abosh, marcin, ashoat

Reviewed By: ashoat

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D5266