Add debug-server task to make file to run mattermost using delve (#9290)

Makefile

@@ -46,6 +46,7 @@ endif
 GOPATH ?= $(shell go env GOPATH)
 GOFLAGS ?= $(GOFLAGS:)
 GO=go
+DELVE=dlv
 GO_LINKER_FLAGS ?= -ldflags \
 				   "-X github.com/mattermost/mattermost-server/model.BuildNumber=$(BUILD_NUMBER)\
 				    -X 'github.com/mattermost/mattermost-server/model.BuildDate=$(BUILD_DATE)'\
@@ -390,6 +391,15 @@ run-server: start-docker ## Starts the server.
 	mkdir -p $(BUILD_WEBAPP_DIR)/dist/files
 	$(GO) run $(GOFLAGS) $(GO_LINKER_FLAGS) $(PLATFORM_FILES) --disableconfigwatch &
 
+debug-server: start-docker
+	mkdir -p $(BUILD_WEBAPP_DIR)/dist/files
+	$(DELVE) debug $(PLATFORM_FILES) --build-flags="-ldflags '\
+		-X github.com/mattermost/mattermost-server/model.BuildNumber=$(BUILD_NUMBER)\
+		-X \"github.com/mattermost/mattermost-server/model.BuildDate=$(BUILD_DATE)\"\
+		-X github.com/mattermost/mattermost-server/model.BuildHash=$(BUILD_HASH)\
+		-X github.com/mattermost/mattermost-server/model.BuildHashEnterprise=$(BUILD_HASH_ENTERPRISE)\
+		-X github.com/mattermost/mattermost-server/model.BuildEnterpriseReady=$(BUILD_ENTERPRISE_READY)'"
+
 run-cli: start-docker ## Runs CLI.
 	@echo Running mattermost for development
 	@echo Example should be like 'make ARGS="-version" run-cli'