Rename a parameter.

This seems to be a typo. `singletree` doesn't make sense, and everywhere
else it is `singlethread`.

Author: nnethercote

compiler/rustc_codegen_llvm/src/back/owned_target_machine.rs

@@ -30,7 +30,7 @@ impl OwnedTargetMachine {
         data_sections: bool,
         unique_section_names: bool,
         trap_unreachable: bool,
-        singletree: bool,
+        singlethread: bool,
         verbose_asm: bool,
         emit_stack_size_section: bool,
         relax_elf_relocations: bool,
@@ -62,7 +62,7 @@ impl OwnedTargetMachine {
                 data_sections,
                 unique_section_names,
                 trap_unreachable,
-                singletree,
+                singlethread,
                 verbose_asm,
                 emit_stack_size_section,
                 relax_elf_relocations,