--with-alt-jar support

[Joshua Sumali]

Hi,

When building the JDK, a bit of time is spent building rt.jar, and I 
think this may be really evident on the non x86/x86_64 archs. So ... 
I've recently added a new option to ./configure: 
--with-alt-jar=</path/to/jar>. This uses the specified jar command 
instead of using the bootstrap jar via the jvm. I've tested this out 
with fastjar (a modified, more openjdk-compatible fastjar -- I still 
have to post the patch...) and here are the results:

x86_64 regular build: 15m 53s
x86_64 --with-alt-jar=/usr/loca/bin/fastjar: 12m 51s

x86 regular build: 47m 58s
x86 --with-alt-jar=/usr/loca/bin/fastjar: 41m 21s

I'm kinda curious to see how much faster builds go on the other platforms :)

Cheers,
Josh