Fix LLVM thread names on Windows.

PR rust-lang#112946 tweaked the naming of LLVM threads, but messed things up
slightly, resulting in threads on Windows having names like `optimize
module {} regex.f10ba03eb5ec7975-cgu.0`.

This commit removes the extraneous `{} `.

Author: nnethercote

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -740,9 +740,9 @@ impl<B: WriteBackendMethods> WorkItem<B> {
         }
 
         match self {
-            WorkItem::Optimize(m) => desc("opt", "optimize module {}", &m.name),
-            WorkItem::CopyPostLtoArtifacts(m) => desc("cpy", "copy LTO artifacts for {}", &m.name),
-            WorkItem::LTO(m) => desc("lto", "LTO module {}", m.name()),
+            WorkItem::Optimize(m) => desc("opt", "optimize module", &m.name),
+            WorkItem::CopyPostLtoArtifacts(m) => desc("cpy", "copy LTO artifacts for", &m.name),
+            WorkItem::LTO(m) => desc("lto", "LTO module", m.name()),
         }
     }
 }