Fixes non deterministic builds by ensuring file compilation order

[ospfranco]

Fixes mlua-rs/mlua#644

After much tweaking around we discovered the source of nondeterminism lies in the way mlua compiles the luau sources. read_dir is nondeterministic in the order of files it returns as it depends on disk IO. This for some reason caused different binary outputs on the final binary compiled by Rust.

You can try this yourself in a Docker image or similar ubuntu machines. Compiling a crate that uses mlua and then getting the sha256 of the final Rust binary. Even though the code and environment is the same, the SHA256 output is different.

For us this caused SGX generating different signatures for the binaries we had produced. Via much tweaking of the compilation process we finally stumbled into the answer.

BTW we only need luau, but this is happening with the lua-src-rs crate as well.

[khvzak]

Thank you! Well done figuring this out.

[ospfranco]

Thank you for merging @khvzak . Could you please let me know when you do a mlua release with the fix?

[khvzak]

I can release this crate ~today. No need to wait for mlua. It’s a subdependency, so you can set a specific version in Cargo.toml and mlua will use it

[ospfranco]

yeah, that would be great, thanks