update the makefiles to allow docker image cache usage based on env var
diff --git a/containers/postgresql/Makefile b/containers/postgresql/Makefile
index ed939d5..38f159c 100644
--- a/containers/postgresql/Makefile
+++ b/containers/postgresql/Makefile
@@ -1,8 +1,9 @@
 IMAGE_NAME:=xosproject/xos-postgress
 CONTAINER_NAME:=xos-db-postgress
+NO_DOCKER_CACHE?=false
 
 .PHONY: build
-build: ; docker build --rm -t ${IMAGE_NAME} .
+build: ; docker build --no-cache=${NO_DOCKER_CACHE} --rm -t ${IMAGE_NAME} .
 
 .PHONY: run
 run: ; docker run -d -p 5432:5432 --name ${CONTAINER_NAME} ${IMAGE_NAME}
diff --git a/containers/synchronizer/Makefile b/containers/synchronizer/Makefile
index ebfe5ef..8620438 100644
--- a/containers/synchronizer/Makefile
+++ b/containers/synchronizer/Makefile
@@ -1,8 +1,9 @@
 IMAGE_NAME:=xosproject/xos-synchronizer-openstack
 CONTAINER_NAME:=xos-synchronizer
+NO_DOCKER_CACHE?=false
 
 .PHONY: build
-build: ; docker build --rm -t ${IMAGE_NAME} .
+build: ; docker build --no-cache=${NO_DOCKER_CACHE} --rm -t ${IMAGE_NAME} .
 
 .PHONY: run
 run: ; docker run -d --name ${CONTAINER_NAME} ${IMAGE_NAME}
diff --git a/containers/xos/Makefile b/containers/xos/Makefile
index a4ffb17..be066ef 100644
--- a/containers/xos/Makefile
+++ b/containers/xos/Makefile
@@ -1,9 +1,10 @@
 CONTAINER_NAME:=xos-server
 IMAGE_NAME:=xosproject/xos
 TOSCA_CONFIG_PATH:=/opt/xos/configurations/opencloud/opencloud.yaml
+NO_DOCKER_CACHE?=false
 
 .PHONY: build
-build: ; docker build --rm -t ${IMAGE_NAME} . && ./initdb
+build: ; docker build --no-cache=${NO_DOCKER_CACHE} --rm -t ${IMAGE_NAME} . && ./initdb
 
 .PHONY: run
 run: ; docker run -d --name ${CONTAINER_NAME} -p 80:8000 ${IMAGE_NAME}