Fix some TODOs in the yasm build.

build/linux/unbundle/yasm.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 if (current_cpu == "x86") {
   _yasm_flags = [
     "-felf32",
     "-m",
     "x86",
   ]
@@ skipping 54 matching lines @@
 
     # Extra defines.
     if (defined(invoker.defines)) {
       foreach(def, invoker.defines) {
         args += [ "-D$def" ]
       }
     }
 
     # Output file.
     outputs = [
-      "$target_out_dir/{{source_name_part}}.o",
+      "$target_out_dir/$source_set_name/{{source_name_part}}.o",
     ]
     args += [
       "-o",
       rebase_path(outputs[0], root_build_dir),
       "{{source}}",
     ]
 
     # The wrapper script run_yasm will write the depfile to the same name as
     # the output but with .d appended (like gcc will).
     depfile = outputs[0] + ".d"
   }
 
   # Gather the .o files into a linkable thing. This doesn't actually link
   # anything (a source set just compiles files to link later), but will pass
   # the object files generated by the action up the dependency chain.
   source_set(source_set_name) {
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
 
     sources = get_target_outputs(":$action_name")
 
     deps = [
       ":$action_name",
     ]
   }
 }