EVM/scripts: build reproducible wasm and preimages

What

Fix #6206 (closed)

This MR provides a script to build the evm kernel wasm files and preimages through a docker container, allowing reproducible builds.

Why

Sofar the preimages and wasm files are only given through https://snapshots.eu.tzinit.org/etherlink-ghostnet/index.html, it hurts a bit the decentralization.

How

To build the kernel, we use the rust-toolchain image stored in gitlab registry (this is done through arguments, so it can be changed if needed) and force the docker platform to be always linux/x86_64 which make, e.g., docker for mac use emulation.

Manually testing the MR

you can run the script:

etherlink/scripts/build-wasm.sh

you should get an output directory: etherlink/kernels-$COMMIT with the wasm files and the preimages.

The sha256 hash of the wasm file (obtained with sha256sum evm_kernel.wasm) should be (on any architecture):

02143db5a90e204ecac9d4c2b623ebb0395507071f236c57bd63bc426ee346b7

Following

The next job is to run this job in the CI and put the directory as artifact.

Checklist

• Document the interface of any function added or modified (see the coding guidelines)
• Document any change to the user interface, including configuration parameters (see node configuration)
• Provide automatic testing (see the testing guide).
• For new features and bug fixes, add an item in the appropriate changelog (docs/protocols/alpha.rst for the protocol and the environment, CHANGES.rst at the root of the repository for everything else).
• Select suitable reviewers using the Reviewers field below.
• Select as Assignee the next person who should take action on that MR