Squashed 'release-tools/' changes from c6a88c6..86ff580

86ff580 Merge pull request kubernetes-csi#116 from andyzhangx/export-image-name
c3a9662 allow export image name and registry name

git-subtree-dir: release-tools
git-subtree-split: 86ff580

build.make

@@ -20,7 +20,7 @@
 
 # This is the default. It can be overridden in the main Makefile after
 # including build.make.
-REGISTRY_NAME=quay.io/k8scsi
+REGISTRY_NAME?=quay.io/k8scsi
 
 # Can be set to -mod=vendor to ensure that the "vendor" directory is used.
 GOFLAGS_VENDOR=