[alfred][git] don't break the plist cleaning on Linux

bin/alfredworkflow.clean

@@ -10,6 +10,8 @@ ensure
 end
 
 plist = ARGF.read
+puts plist and exit unless File.exist?("/usr/libexec/PlistBuddy")
+
 with_tempfile('info.plist') do |f|
   f << plist
   f.flush