Build.rs might be able to make build process easier.

[Naoaki Iwakiri]

This project now relies on cargo-c and cbindgen to generate C header and lib

On readme it introduces to install them in the env and run those specific commands, but cargo has build.rs build script feature to run on cargo build.

We may be able to avoid running external program and use other crates in build scripts.

Expected feature:

Without installing cbindgen and cargo-c in the environment, just running cargo build ( with some flags ) automatically generates header files and c shared object library.