message: Document NSS_DIR
  Closes
diff: @@ -14,3 +14,10 @@ To run test http 3 programs (neqo-client and neqo-http3-server):
  * `./target/debug/neqo-http3-server [::]:12345 --db ./test-fixture/db`
  * `./target/debug/neqo-client http://127.0.0.1:12345/ --db ./test-fixture/db`
  +## Faster Builds with Separate NSS/NSPR
  +
  +You can clone NSS (https://hg.mozilla.org/projects/nss) and NSPR
  +(https://hg.mozilla.org/projects/nspr) into the same directory and export an
  +enviroment variable called `NSS_DIR` pointing to NSS. This causes the build to
  +use the existing NSS checkout.
  +
  