Fix package fetching
Fix package fetching

Two issues got fixed:
* The variable name for the package file got changed to PKG_FILE2
  to avoid conflicts with the PKG_FILE from previous erlang.mk versions.
* The way repositories are fetched changed to fix an issue preventing
  fetching the package file *and* the repositories on the same invokation.

michaelnisi/erlang.mk,yannayl/erlang.mk,ingwinlu/erlang.mk,a12n/erlang.mk,KrzysiekJ/erlang.mk,nevar/erlang.mk,layerhq/erlang.mk,crownedgrouse/erlang.mk,ninenines/erlang.mk,bsmr-erlang/erlang.mk,rabbitmq/erlang.mk,efcasado/erlang.mk,hairyhum/erlang.mk,dch/erlang.mk,jj1bdx/erlang.mk