* common.mk (prelude.c): add dependency to LIB_SRCS because
  enc/prelude.rb requires lib/unicode_normalize.rb, and it's also
  requires lib/unicode_normalize/tables.rb (=LIB_SRCS).


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48096 b2dd03c8-39d4-4d8f-98ff-823fe69b080e