bootstrap: better warning fix (Thanks James Fish)
bootstrap: better warning fix (Thanks James Fish)

As a follow-up to bad3a795, implement a better fix for the pre-18.0
warning.

erlang:now/0 was deprecated in 18.0, and as the escript has to pass
erl_lint:module/1 (even without -mode(compile)), we would see a
deprecation warning for erlang:now/1.  One solution is to use
-compile({nowarn_deprecated_function, [{erlang, now, 0}]}), but that
would raise a warning in versions older than 18.0. Calling erlang:now/0
via apply/3 avoids that.

macintux/rebar,norton/rebar,CMoH/rebar,bsmr-erlang/rebar,scatterbrain/rebar,bsmr-erlang/rebar,rebar/rebar,matwey/rebar,bsmr-erlang/rebar,cloudant/couchdb-rebar,oubiwann/rebar,paulo-ferraz-oliveira/rebar,K2InformaticsGmbH/rebar,SiDen/rebar,rebar/rebar,choptastic/rebar,scatterbrain/rebar,shkumagai/rebar,jacktang/rebar,apache/couchdb-rebar,lrascao/rebar,bsmr-erlang/rebar,shkumagai/rebar,beni55/rebar,paulo-ferraz-oliveira/rebar,csyangchen/rebar,beni55/rebar,lrascao/rebar,CMoH/rebar,K2InformaticsGmbH/rebar,evnix/rebar,norton/rebar,macintux/rebar,SiDen/rebar,oubiwann/rebar,choptastic/rebar,K2InformaticsGmbH/rebar,choptastic/rebar,jacktang/rebar,platinumthinker/rebar,platinumthinker/rebar,GabrielNicolasAvellaneda/rebar,paulo-ferraz-oliveira/rebar,lpgauth/rebar,lrascao/rebar,platinumthinker/rebar,oubiwann/rebar,GabrielNicolasAvellaneda/rebar,csyangchen/rebar,evnix/rebar,SiDen/rebar,matwey/rebar,rebar/rebar,cloudant/couchdb-rebar,jacktang/rebar,matwey/rebar,K2InformaticsGmbH/rebar,cloudant/couchdb-rebar,dcarastan/rebar,macintux/rebar,lpgauth/rebar,csyangchen/rebar,lrascao/rebar,dcarastan/rebar,matwey/rebar,CMoH/rebar,shkumagai/rebar,GabrielNicolasAvellaneda/rebar,beni55/rebar,apache/couchdb-rebar,apache/couchdb-rebar,lrascao/rebar,dcarastan/rebar,K2InformaticsGmbH/rebar,evnix/rebar,matwey/rebar,norton/rebar,lpgauth/rebar,scatterbrain/rebar,norton/rebar