Check Wasm module reproducibility

[ipetr0v]

We need to check if Oak Wasm modules have the same hash after a rebuild (reproducibility).
In order to check we need clear the Cargo cache before rebuilding (so it would not influence the build).
Also we should check the hash values of modules compiled on different machines.

It also could be done as a part of the CI, but it might affect the Cloud Build time, since we will be clearing Cargo cache for all applications.

cc @tiziano88

[ipetr0v]

My sha256sum values for the hello_world example look as follows:

3b65e7dcfeec0e6c979e69176169e6c235f2fffb95afb818f5c37cb5c545908c  target/wasm32-unknown-unknown/release/hello_world.wasm

3b65e7dcfeec0e6c979e69176169e6c235f2fffb95afb818f5c37cb5c545908c  target/wasm32-unknown-unknown/release/hello_world.wasm

And the hash value from a different machine:

3b65e7dcfeec0e6c979e69176169e6c235f2fffb95afb818f5c37cb5c545908c  target/wasm32-unknown-unknown/release/hello_world.wasm

So everything looks fine.

[tiziano88]

Great news!

[tiziano88]

So actually #865 is a duplicate of this, but I guess I'll keep that open since it has a bit more context about the reproducibility issues.