cleanup implementation

* remove commented out line
* remove 'format' references that are no longer possible

rust/private/lto.bzl

@@ -66,8 +66,6 @@ def _determine_lto_object_format(ctx, toolchain, crate_info):
         return "only_object"
 
     perform_linking = crate_info.type in ["bin", "staticlib", "cdylib"]
-
-    # is_linkable = crate_info.type in ["lib", "rlib", "dylib", "proc-macro"]
     is_dynamic = crate_info.type in ["dylib", "cdylib", "proc-macro"]
     needs_object = perform_linking or is_dynamic
 
@@ -107,10 +105,10 @@ def construct_lto_arguments(ctx, toolchain, crate_info):
     if mode in ["thin", "fat", "off"] and not is_exec_configuration(ctx):
         args.append("lto={}".format(mode))
 
-    if format in ["unspecified", "object_and_bitcode"]:
+    if format == "object_and_bitcode":
         # Embedding LLVM bitcode in object files is `rustc's` default.
         args.extend([])
-    elif format in ["off", "only_object"]:
+    elif format == "only_object":
         args.extend(["embed-bitcode=no"])
     elif format == "only_bitcode":
         args.extend(["linker-plugin-lto"])