sysutils/consul-replicate: Unbreak build with Go 1.12

• Remove GOCACHE=off as build cache is required starting from Go 1.12 [1]
• Pass MAKE_ENV (so GOCACHE defaults to $WRKDIR/.cache)

[1] https://tip.golang.org/doc/go1.12#gocache

PR: 236033
Submitted by: Dmitri Goutnik <dg@syrec.org>
Approved by: jhixson (maintainer)