added platform check and message for none nix systems

git-svn-id: file:///home/svn/framework3/trunk@13365 4d416f70-5f16-0410-b530-b9f4589650da

modules/post/multi/gather/ssh_creds.rb

@@ -52,6 +52,9 @@ class Metasploit3 < Msf::Post
 		if paths.nil?
 			print_error("No users found with a .ssh directory")
 			return
+		else
+			print_error("Platfor is not Unix or Linux based.")
+			return
 		end
 
 		download_loot(paths)