template/prelude.c.tmpl

* template/prelude.c.tmpl: move from tool/compile_prelude.rb and
  expand by generic_erb.rb.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48373 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
common.mk: preludes

* common.mk (preludes): make prelude.c too.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48374 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
make-snapshot: no wait unless needed

* tool/make-snapshot (package): no wait when using already
  exported source without modification, assuming exported 2
  seconds (the lowest timestamp resolution) ago or more.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48375 b2dd03c8-39d4-4d8f-98ff-823fe69b080e