build stop early if apk add fails

appveyor.yml

@@ -27,7 +27,9 @@ test_script:
 
 on_success:
   - sh: |
-      apk add curl jq
+      if [ ! apk add curl jq ]; then
+        exit 1
+      fi
       CURR_VER=$(cat package.json | jq -r .version)
       if curl -s -X GET -H "Authorization: token $deploytoken" https://git.nfp.is/api/v1/repos/$APPVEYOR_REPO_NAME/releases | grep -o "\"name\"\:\"v${CURR_VER}\"" > /dev/null; then
         echo "Release already exists, nothing to do.";