common.mk: make sizes.c with MINIRUBY

* common.mk (sizes.c): use MINIRUBY because Init_sizes() for miniruby
  is defined in miniinit.c and miniruby does not depend on this file.
  [Bug #8968]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43137 b2dd03c8-39d4-4d8f-98ff-823fe69b080e