Make RubyGems generate sane binaries that work for ruby18 and ruby19

gistfile1.diff

--- a/lib/rubygems/installer.rb	2009-05-02 18:53:50.000000000 -0400
+++ b/lib/rubygems/installer.rb	2009-06-11 16:25:33.000000000 -0400
@@ -397,14 +397,19 @@
     else
       path = File.join @gem_dir, @spec.bindir, bin_file_name
 
+      ruby_bin_file = File.join(File.dirname(Gem.ruby), 'ruby')
+      unless File.symlink?(ruby_bin_file)
+        ruby_bin_file = Gem.ruby
+      end
+
       File.open(path, "rb") do |file|
         first_line = file.gets
         if first_line =~ /^#!/ then
           # Preserve extra words on shebang line, like "-w".  Thanks RPA.
-          shebang = first_line.sub(/\A\#!.*?ruby\S*/, "#!#{Gem.ruby}")
+          shebang = first_line.sub(/\A\#!.*?ruby\S*/, "#!#{ruby_bin_file}")
         else
           # Create a plain shebang line.
-          shebang = "#!#{Gem.ruby}"
+          shebang = "#!#{ruby_bin_file}"
         end
 
         shebang.strip # Avoid nasty ^M issues.