Use specific pprof-nodejs branch for testing while release is not done

Author: nsavoire

package.json

@@ -6,6 +6,7 @@
   "typings": "index.d.ts",
   "scripts": {
     "preinstall": "node scripts/preinstall.js",
+    "postinstall": "PREBUILD=1 npm install --no-save --no-package-lock Datadog/pprof-nodejs#nsavoire/test_prepack",
     "bench": "node benchmark",
     "bench:profiler": "node benchmark/profiler",
     "bench:e2e": "SERVICES=mongo yarn services && cd benchmark/e2e && node benchmark-run.js --duration=30",