Fix graphdriver lookup in makefile

When graphdriver is not provided the graphdriver is looked up
from docker info, but without quotes it may fail and set the
graphdriver to an incorrect value.

Signed-off-by: Derek McGowan <derek@mcg.dev>

Makefile

@@ -4,7 +4,7 @@ DOCKER ?= docker
 BUILDX ?= $(DOCKER) buildx
 
 # set the graph driver as the current graphdriver if not set
-DOCKER_GRAPHDRIVER := $(if $(DOCKER_GRAPHDRIVER),$(DOCKER_GRAPHDRIVER),$(shell docker info -f {{ .Driver }} 2>&1))
+DOCKER_GRAPHDRIVER := $(if $(DOCKER_GRAPHDRIVER),$(DOCKER_GRAPHDRIVER),$(shell docker info -f '{{ .Driver }}' 2>&1))
 export DOCKER_GRAPHDRIVER
 
 DOCKER_GITCOMMIT := $(shell git rev-parse HEAD)