Reformat use declarations.

The previous commit updated `rustfmt.toml` appropriately. This commit is
the outcome of running `x fmt --all` with the new formatting options.

compiler/rustc_codegen_gcc/src/gcc_util.rs

@@ -1,11 +1,10 @@
 #[cfg(feature = "master")]
 use gccjit::Context;
-use smallvec::{smallvec, SmallVec};
-
 use rustc_data_structures::fx::FxHashMap;
 use rustc_middle::bug;
 use rustc_session::Session;
 use rustc_target::target_features::RUSTC_SPECIFIC_FEATURES;
+use smallvec::{smallvec, SmallVec};
 
 use crate::errors::{
     PossibleFeature, TargetFeatureDisableOrEnable, UnknownCTargetFeature,