Passing rustfmt.toml to build

[grantchristophera]

Hi,

I was trying to build https://github.com/Pumpkin-MC/Pumpkin which uses a build script for one of it's crates. The script makes a call to rustfmt, which ordinarily would find rustfmt.toml in the top directory of the project, but I guess it's not copied or something when building in naersk. I added an explicit argument for my purposes atm as a workaround.

[nmattia]

@grantchristophera that's an interesting use case, can you explain how rustfmt is used at build time? If this is somewhat common we could add an example to the README