Building with build.rs

[max-sixty]

Is there any facility for building wasm binaries within build.rs, rather than calling into wasm-bindgen's CLI?

Over at PRQL/prql#2881 we're hoping to use a build.rs file to build our wasm binaries, mostly to take advantage of cargo's caching — wasm-pack seems to require a full rebuild even if no files have changed.

We're planning to use https://crates.io/crates/substrate-wasm-builder. That seems to allow building from build.rs. It's less focused on JS projects though, so probably need additional CLI calls into wasm-bindgen.

I also found https://github.com/rustminded/xtask-wasm/blob/main/src/dist.rs which also looks interesting, but doesn't seem to support building from build.rs.

(I also posted this at rustwasm/wasm-pack#916, so feel free to close if that's a better place for it)

Thank you!