[vtctldclient] Restructure code organization for doing codegen on a local client

Signed-off-by: Andrew Mason <amason@slack-corp.com>

Makefile

@@ -126,8 +126,8 @@ install-testing: build
 	mkdir -p "$${PREFIX}/web/vtctld2"
 	cp -R web/vtctld2/app "$${PREFIX}/web/vtctld2"
 
-grpcvtctldclient: go/vt/proto/vtctlservice/vtctlservice.pb.go
-	make -C go/vt/vtctl/grpcvtctldclient
+vtctldclient: go/vt/proto/vtctlservice/vtctlservice.pb.go
+	make -C go/vt/vtctl/vtctldclient
 
 parser:
 	make -C go/vt/sqlparser

go/vt/vtctl/grpcvtctldclient/client.go

@@ -35,7 +35,7 @@ type gRPCVtctldClient struct {
 	c  vtctlservicepb.VtctldClient
 }
 
-//go:generate -command grpcvtctldclient go run ./codegen
+//go:generate -command grpcvtctldclient go run ../vtctldclient/codegen
 //go:generate grpcvtctldclient -out client_gen.go
 
 func gRPCVtctldClientFactory(addr string) (vtctldclient.VtctldClient, error) {

go/vt/vtctl/vtctldclient/Makefile

@@ -14,6 +14,8 @@
 
 MAKEFLAGS = -s
 
-generate:
-	go generate ./...
-	gofmt -w client_gen.go
+all: grpcvtctldclient
+
+grpcvtctldclient:
+	go generate ../$@/...
+	gofmt -w ../$@/client_gen.go