Wrong default GEM_HOME in generated META-INF/init.rb

Was generating the following: (default config.gem_path is WEB-INF/gems though)

if $servlet_context.nil?
  ENV['GEM_HOME'] = File.expand_path('../../WEB-INF', __FILE__)
  ...

After:

if $servlet_context.nil?
  ENV['GEM_HOME'] = File.expand_path(File.join('..', '..', '/WEB-INF/gems'), __FILE__)
  ...