Add an option to automatically run wasm-opt on wasm binaries

[Jacalz]

It is possible to optimize WASM binaries after they have been built using something like wasm-opt. There are various modes and different kind of optimizations that can be done (size, speed and some things not enabled by default etc.). We should investigate if this is viable to add in some way in order to improve performance. I am worried that this might take a long time to run.