chore: fix build post test by cleaning temp test output

This is a quick workaround. A better solution is to improve test logic
so these folders never exist/remain.

Author: jasonkuhrt

packages/graphqlgen/package.json

@@ -13,9 +13,10 @@
     "gg": "dist/index.js"
   },
   "scripts": {
+    "clean": "rm -rf ./src/tests/**/tmp && rm -rf ./src/tests/**/generated",
     "prepublish": "rm -rf example/node_modules && npm test && npm run build",
     "benchmarks": "ts-node benchmarks",
-    "build": "npm run lint && tsc --declaration",
+    "build": "npm run clean && npm run lint && tsc --declaration",
     "watch": "tsc -w",
     "lint": "tslint --project tsconfig.json {src,test}/**/*.ts",
     "test": "jest",