fix node artifact building on mac
diff --git a/tools/run_tests/build_artifact_node.sh b/tools/run_tests/build_artifact_node.sh
index ec3fb64..8aeec79 100755
--- a/tools/run_tests/build_artifact_node.sh
+++ b/tools/run_tests/build_artifact_node.sh
@@ -28,8 +28,12 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+NODE_TARGET_ARCH=$1
+source ~/.nvm/nvm.sh
 set -ex
 
+nvm use 4
+
 cd $(dirname $0)/../..
 
 rm -rf build
@@ -42,6 +46,6 @@
 
 for version in ${node_versions[@]}
 do
-  node-pre-gyp configure rebuild package testpackage --target=$version --target_arch=$1
+  node-pre-gyp configure rebuild package testpackage --target=$version --target_arch=$NODE_TARGET_ARCH
   cp -r build/stage/* artifacts/
 done