Use existing goimports installation if available

cmd/urfave-cli-genflags/Makefile

@@ -1,6 +1,9 @@
+GOIMPORTS_BIN ?= $(shell which goimports || true)
 GOTEST_FLAGS ?= -v --coverprofile main.coverprofile --covermode count --cover github.com/urfave/cli/v2/cmd/urfave-cli-genflags
 GOBUILD_FLAGS ?= -x
 
+export GOIMPORTS_BIN
+
 .PHONY: all
 all: test build smoke-test
 

cmd/urfave-cli-genflags/main.go

@@ -95,6 +95,7 @@ func main() {
 			},
 			&cli.PathFlag{
 				Name:    "goimports",
+				EnvVars: []string{"GOIMPORTS_BIN"},
 				Value:   filepath.Join(top, ".local/bin/goimports"),
 			},
 		},