add Builder#standard_threaded_build, #standard_finalize

parallelize Program builder command

lib/rscons/builders/object.rb

@@ -96,15 +96,7 @@ module Rscons
           v.nil? and raise "Error: unknown input file type: #{sources.first.inspect}"
         end.first
         command = env.build_command("${#{com_prefix}CMD}", vars)
-        if cache.up_to_date?(target, command, sources, env)
-          target
-        else
-          cache.mkdir_p(File.dirname(target))
-          FileUtils.rm_f(target)
-          ThreadedCommand.new(
-            command,
-            short_description: "#{com_prefix} #{target}")
-        end
+        standard_threaded_build("#{com_prefix} #{target}", target, command, sources, env, cache)
       end
 
       # Finalize the build operation.

lib/rscons/builders/program.rb

@@ -83,8 +83,20 @@ module Rscons
           '_SOURCES' => objects,
           'LD' => ld,
         })
+        options[:sources] = objects
         command = env.build_command("${LDCMD}", vars)
-        standard_build("LD #{target}", target, command, objects, env, cache)
+        standard_threaded_build("LD #{target}", target, command, objects, env, cache)
+      end
+
+      # Finalize a build.
+      #
+      # @param options [Hash]
+      #   Finalize options.
+      #
+      # @return [String, nil]
+      #   The target name on success or nil on failure.
+      def finalize(options)
+        standard_finalize(options)
       end
 
     end