THRIFT-5621: Add Swift tutorial

Client: swift
diff --git a/tutorial/Makefile.am b/tutorial/Makefile.am
index aa5712b..24969d1 100644
--- a/tutorial/Makefile.am
+++ b/tutorial/Makefile.am
@@ -86,6 +86,10 @@
 SUBDIRS += php
 endif
 
+if WITH_SWIFT
+SUBDIRS += swift
+endif
+
 #
 # generate html for tutorial.thrift
 #