Modify the Rakefile to support a jgem install.

Rakefile

@@ -64,7 +64,8 @@ at_exit { File.delete('REVISION') rescue nil }
 desc "Install Haml as a gem."
 task :install => [:package] do
   sudo = RUBY_PLATFORM =~ /win32/ ? '' : 'sudo'
-  sh %{#{sudo} gem install --no-ri pkg/haml-#{File.read('VERSION').strip}}
+  gem  = RUBY_PLATFORM =~ /java/  ? 'jgem' : 'gem' 
+  sh %{#{sudo} #{gem} install --no-ri pkg/haml-#{File.read('VERSION').strip}}
 end
 
 desc "Release a new Haml package to Rubyforge. Requires the NAME and VERSION flags."
@@ -181,4 +182,4 @@ namespace :test do
       `rm -rf test/rails`
     end
   end
-end
+end