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_llvm/src/lib.rs

@@ -7,10 +7,11 @@
 
 // NOTE: This crate only exists to allow linking on mingw targets.
 
-use libc::{c_char, size_t};
 use std::cell::RefCell;
 use std::slice;
 
+use libc::{c_char, size_t};
+
 #[repr(C)]
 pub struct RustString {
     pub bytes: RefCell<Vec<u8>>,