Update npm when building Node artifacts

tools/run_tests/artifacts/build_artifact_node.bat

@@ -35,6 +35,8 @@ set PATH=%PATH%;C:\Program Files\nodejs\;%APPDATA%\npm
 
 del /f /q BUILD || rmdir build /s /q
 
+call npm update -g npm
+
 call npm update || goto :error
 
 mkdir -p %ARTIFACTS_OUT%

tools/run_tests/artifacts/build_artifact_node.sh

@@ -34,6 +34,8 @@ source ~/.nvm/nvm.sh
 nvm use 4
 set -ex
 
+npm update -g npm
+
 cd $(dirname $0)/../../..
 
 rm -rf build || true