ci: log make vars before build

Jenkinsfile

@@ -136,6 +136,21 @@ spec:
 
             export DOCKER_BUILDKIT=1
 
+            echo "Sanity-checking Makefile vars..."
+            make -n \
+              VERSIONTAG="${VERSIONTAG}" \
+              BASEIMAGETAG="${VERSIONTAG}" \
+              IMAGENAMESPACE="${IMAGE_NAMESPACE}" \
+              BASEIMAGENAMESPACE="${IMAGE_NAMESPACE}" \
+              DOCKERNETWORK=host \
+              PULL_BASE_FROM_DOCKERHUB=false \
+              BUILD_BASE=true \
+              BUILDTRIVYADP=false \
+              BUILD_INSTALLER=true \
+              build \
+              | grep -E 'make -f .*/make/photon/Makefile build|IMAGENAMESPACE=|BASEIMAGENAMESPACE=|VERSIONTAG=|BASEIMAGETAG=|PULL_BASE_FROM_DOCKERHUB=' \
+              || true
+
             # Harbor's root Makefile hard-sets many defaults (e.g. IMAGENAMESPACE=goharbor,
             # PULL_BASE_FROM_DOCKERHUB=true). Environment exports are not sufficient because
             # makefile assignments override the environment. Pass overrides on the make