Mistakes in 'Build Script' docs

[alexreg]

1. The sentence

Any other element is a user-defined metadata that will be passed to dependencies.

should instead read

Any other element is a user-defined metadata that will be passed to *dependents*.

2. The sentence

We’ve also seen a brief example of how a build script can use a crate as a dependency purely for the build process and not for the crate itself at runtime.

should appear at the end of the 2nd case study, not the 1st, where it clearly doesn't apply.

[carols10cents]

It looks like this was fixed in rust-lang/cargo#3286; I'm guessing cross-repo "fixes" doesn't automatically close issues :) Please reopen if I'm mistaken! ❤️

[alexreg]

Thanks!