Make Dfx build command build canisters in parallel

[ByronBecker]

For larger projects, it can take on the order of minutes to build a larger canister. Projects with 7-10 canisters then take a long time to build, especially if one wants to spin up a local environment for testing or frontend development.

It would be much faster if running dfx build would build all canisters in the project in parallel.

[chenyan-dfinity]

I encourage you to try https://github.com/chenyan2002/mops-cli. Just run mops-cli build main.mo to build the canister. If you want to parallelize it, you can put them in a bash script.