not walking directory if KUBE_BUILD_PLATFORMS is given

build/lib/release.sh

@@ -125,8 +125,13 @@ function kube::release::package_src_tarball() {
 # Package up all of the cross compiled clients. Over time this should grow into
 # a full SDK
 function kube::release::package_client_tarballs() {
-   # Find all of the built client binaries
-  for platform_long in "${LOCAL_OUTPUT_BINPATH}"/*/*; do
+  # Find all of the built client binaries
+  local long_platforms=("${LOCAL_OUTPUT_BINPATH}"/*/*)
+  if [[ -n ${KUBE_BUILD_PLATFORMS-} ]]; then
+    read -ra long_platforms <<< "${KUBE_BUILD_PLATFORMS}"
+  fi
+
+  for platform_long in "${long_platforms[@]}"; do
     local platform
     local platform_tag
     platform=${platform_long##${LOCAL_OUTPUT_BINPATH}/} # Strip LOCAL_OUTPUT_BINPATH