Build install summary in a separate method and print all at once

This prevents interleaved output, e.g. when running with Ruby warnings
turned on.

Library/Homebrew/formula_installer.rb

@@ -319,16 +319,23 @@ def finish
     post_install
 
     ohai "Summary" if ARGV.verbose? or show_summary_heading
-    unless ENV['HOMEBREW_NO_EMOJI']
-      print "#{ENV['HOMEBREW_INSTALL_BADGE'] || "\xf0\x9f\x8d\xba"}  " if MacOS.version >= :lion
-    end
-    print "#{f.prefix}: #{f.prefix.abv}"
-    print ", built in #{pretty_duration build_time}" if build_time
-    puts
+    puts summary
   ensure
     unlock if hold_locks?
   end
 
+  def emoji
+    ENV['HOMEBREW_INSTALL_BADGE'] || "\xf0\x9f\x8d\xba"
+  end
+
+  def summary
+    s = ""
+    s << "#{emoji}  " if MacOS.version >= :lion and not ENV['HOMEBREW_NO_EMOJI']
+    s << "#{f.prefix}: #{f.prefix.abv}"
+    s << ", built in #{pretty_duration build_time}" if build_time
+    s
+  end
+
   def build_time
     @build_time ||= Time.now - @start_time unless pour_bottle? or ARGV.interactive? or @start_time.nil?
   end