Fail the build if wasm-opt not installed
Created by: ascjones
Currently a warning is displayed if wasm-opt is not installed. However some users are not reading the warning.
Since contract authors would definitely want their contracts optimized (storage rent!), we should fail the build if it is not installed. They won't be able to ignore that.
If for whatever reason they want to still compile without installing wasm-opt, we should provide an option e.g. --no-wasm-opt or --skip-wasm-optimizations
Alternative
Investigate using https://github.com/pepyakin/binaryen-rs as a dependency so as not to require manual installation of wasm-opt