I had the same problem. The binaries on the IBM site do not have the -encoding option enabled. You have to indeed compile jikes yourself. Actually it is quite easy. I had my own jikes build for windows in 10 minutes!! Just follow the steps in as described on http://www-124.ibm.com/developerworks/oss/jikes/faq/dev-win32.shtml
For details please check above page, but short version:
1. Download jikes source code; 2. Install MinGW and MSYS; 3. Download libiconv-1.8.tar.gz; 4. Compile libiconv; 5. Compile jikes;
That's it!. Tip: make sure you use the correct quote (`) not ('), in the make statement at the commandline.
Sector Financial Services Institutes
ADC Technologies (B56)