add reformat support for multiple targets

hardware/Rakefile

@@ -100,10 +100,10 @@ gerbers = targets.collect{|target| GERBERS.collect{|suffix| target[:name]+suffix
 task :gerber => gerbers
 CLOBBER.include(gerbers)
 
-=begin
 desc "reformat gerber and drill output (some programs like LPKF CircuitPro have difficulties with gEDA pcb output)"
-task :reformat => GERBERS do
-  GERBERS.each do |gerber|
+task :reformat => gerbers do
+  gerbers.each do |gerber|
+    next unless File.exist? gerber
     if gerber.end_with? ".gbr" then
       sh "gerbv --export=rs274x --output=#{gerber} #{gerber}"
     elsif gerber.end_with? ".cnc" then
@@ -111,7 +111,6 @@ task :reformat => GERBERS do
     end
   end
 end
-=end
 
 # ================
 # helper functions