RARS RISC-V CPU Simulator support for EJudge contest management system

1. Preparations:
   1. Download RARS Simulator .jar file and install java runtime
   2. Create rars symlink (rars-simulator) for EJudge, e.g.: sudo ln -s '/home/ejudge/rars_1.5.jar' /usr/local/bin/rars-simulator
2. EJudge integration:
   • Put both *.in files in $EJUDGE_PREFIX/libexec/ejudge/lang in (e.g. /home/ejudge/inst-ejudge/libexec/ejudge/lang/in) and run ejudge-setup
   • Or put both *.in files in /home/ejudge/compile/scripts/in and run ejudge-configure-compilers.
3. Update EJudge limits (because RARS is java-based simulator), e.g. for /home/judges/000001/conf/serve.cfg set:

[problem]
max_vm_size = 64G
max_stack_size = 64G
max_file_size = 64G
time_limit = 10

4. References:
   • RARS RISC-V CPU Simulator: https://github.com/TheThirdOne/rars
   • EJudge contest management system: https://github.com/blackav/ejudge
   • EJudge wiki: https://ejudge.ru/wiki/index.php/%D0%A1%D0%B8%D1%81%D1%82%D0%B5%D0%BC%D0%B0_ejudge
5. Some known issues:
   • RARS executes .asm files without this extention incorrectly (e.g. no user input). Maybe they are treated as binary/compiled files?
   • No built-in way in RARS to disable 1st (copyright) & last (exit type) output lines to stdio. Workround is used for now.
   • RARS syscall for reading int's (and other numbers) - no EOF handling