Failure to run build scripts is not visible to the user

[jonas-schievink]

When opening https://github.com/wasm3/wasm3-rs/ in VS Code, rust-analyzer indexes the project successfully, but reports a bogus error in wasm3-sys/src/lib.rs about OUT_DIR not being set. This happens because it failed to fetch the value of OUT_DIR from the build script, since that fails to run when bindgen isn't installed you forget to checkout submodules (I'm not actually sure what happens here).

It would be good to make this error visible, since currently there isn't any indication that the build script didn't succeed.

[jonas-schievink]

Seems like I misdiagnosed this issue, this happens even when cargo build works fine. And for some reason the diagnostic does not show up when just doing env!("OUT_DIR");, it has to be wrapped in some other macro (lazy or eager).

[lnicola]

So maybe it isn't related, but see also #9864.