build: add GOEXPERIMENT=loopvar to build+install directives

The prior commit made sure that no unit tests failed with the new logic
applied. We'll also update our build+install commands so all the
binaries are built with the new loop semantics.

Makefile

@@ -13,8 +13,8 @@ MIGRATE_BIN := $(GO_BIN)/migrate
 
 COMMIT := $(shell git describe --tags --dirty)
 
-GOBUILD := GO111MODULE=on go build -v
-GOINSTALL := GO111MODULE=on go install -v
+GOBUILD := GOEXPERIMENT=loopvar GO111MODULE=on go build -v
+GOINSTALL := GOEXPERIMENT=loopvar GO111MODULE=on go install -v
 GOTEST := GOEXPERIMENT=loopvar GO111MODULE=on go test 
 GOMOD := GO111MODULE=on go mod