RFR(T) : 8225450 : use @file in CtwRunner

[Igor Ignatyev]

http://cr.openjdk.java.net/~iignatyev//8225450/webrev.00/index.html
> 34 lines changed: 5 ins; 0 del; 29 mod; 

Hi all,

could you please review this trivial patch for CtwRunner which makes it more robust?
from JBS:
> I've noticed that CtwRunner might fail when used to compile a big set of jar files on windows due to exceeding command line length limit. the fix is to save command line to a file and pass this file to java launcher as @file.

webrev: http://cr.openjdk.java.net/~iignatyev//8225450/webrev.00/index.html
JBS: https://bugs.openjdk.java.net/browse/JDK-8225450
testing: 
 - test/hotspot/jtreg/applications/ctw/modules
 - manually check that the previously failing execution works on windows

Thanks,
-- Igor