Dockerfile: Avoid hardcoding the kubebuilder version in the build root image

Signed-off-by: timflannagan <[email protected]>

Author: timflannagan

base.Dockerfile

@@ -1,12 +1,12 @@
 # Dockerfile to bootstrap build and test in openshift-ci
-
 FROM openshift/origin-release:golang-1.15
 
+ARG KUBEBUILDER_RELEASE=2.3.1
 # Install test dependencies
 RUN yum install -y skopeo && \
     export OS=$(go env GOOS) && \
     export ARCH=$(go env GOARCH) && \
-    curl -L "https://go.kubebuilder.io/dl/2.3.1/${OS}/${ARCH}" | tar -xz -C /tmp/ && \
-    mv /tmp/kubebuilder_2.3.1_${OS}_${ARCH}/ /usr/local/kubebuilder && \
+    curl -L "https://go.kubebuilder.io/dl/${KUBEBUILDER_RELEASE}/${OS}/${ARCH}" | tar -xz -C /tmp/ && \
+    mv /tmp/kubebuilder_${KUBEBUILDER_RELEASE}_${OS}_${ARCH}/ /usr/local/kubebuilder && \
     export PATH=$PATH:/usr/local/kubebuilder/bin && \
     echo "Kubebuilder installation complete!"