bitlbee: optional otr support

Closes Homebrew#15261.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>

Library/Formula/bitlbee.rb

@@ -6,10 +6,12 @@ class Bitlbee < Formula
   sha1 '74afdff87be49ce060771a6ae10d7643cd57b9b6'
 
   option 'purple', "Use libpurple for all communication with instant messaging networks"
+  option 'with-otr', "Build with otr (off the record) support"
 
   depends_on 'glib'
   depends_on 'gnutls'
-  depends_on 'libpurple' if build.include? 'purple'
+  depends_on 'libpurple' => :optional if build.include? 'purple'
+  depends_on 'libotr' => :optional if build.include? 'with-otr'
 
   def install
     # By default Homebrew will set ENV['LD'] to the same as ENV['CC'] which
@@ -27,6 +29,7 @@ def install
             "--ipsocket=#{var}/bitlbee/run/bitlbee.sock"]
 
     args << "--purple=1" if build.include? "purple"
+    args << "--otr=1" if build.include? "with-otr"
 
     system "./configure", *args