Only check for Jars if lib exists.

Library/Homebrew/install.rb

@@ -158,13 +158,15 @@ def install f
     end
 
     # Check for Jars in lib
+    if File.exist?(f.lib)
       unless f.lib.children.select{|g| g.to_s =~ /\.jar$/}.empty?
-      opoo 'JARs where installed to "lib".'
+        opoo 'JARs were installed to "lib".'
         puts "Installing JARs to \"lib\" can cause conflicts between packages."
         puts "For Java software, it is typically better for the formula to"
         puts "install to \"libexec\" and then symlink or wrap binaries into \"bin\"."
         puts "See \"activemq\", \"jruby\", etc. for examples."
       end
+    end
 
     # link from Cellar to Prefix
     begin