mkarchiso: prevent interference from xorriso startup files
Options set in xorriso startup files (~/.xorrisorc) could interfere with the xorriso command run by mkarchiso. For example, if ~root/.xorrisorc contains -dummy on, then the ISO file will be empty.
Pass -no_rc as the first option to xorriso to prevent interference and unintended behavior.
Fixes #153 (closed).