Rollup merge of #104404 - GuillaumeGomez:fix-missing-minification, r=notriddle

Fix missing minification for static files

It's a fix for https://github.com/rust-lang/rust/pull/101702.

The problem was that `Path::ends_with` doesn't do what we thought it does: it checks if the entire item is the last path part, no just if the "path string" ends with the given argument. So instead, I just used the `extension()` method to get the information we want.

cc `@jsha`
r? `@notriddle`

PS: Is it worth it to add a CI test to ensure that the minification was performed on JS and CSS files or not?