* common.mk: need to quote $BASERUBY because it may includes options.
  this change is only for release management, not bug fix.
  [Backport #9837] [ruby-dev:48218]


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@45941 b2dd03c8-39d4-4d8f-98ff-823fe69b080e