Add script to run headless tests easily

Summary:
It's not obvious how to run the headless tests at the moment, and requires manual steps this adds a script to do it.
It still does not start an emulator or the sample app, but it's an improvement.

Reviewed By: passy

Differential Revision: D17155308

fbshipit-source-id: 846b87389823f422030470807aa4aabacce69179

scripts/run-headless-tests.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+
+set -xeuo pipefail
+
+if [ `adb devices | wc -l` -lt "3" ]
+then
+    echo "No devices are connected. Make sure emulator is booted with flipper sample app running"
+    exit 1
+fi
+
+yarn build-headless --mac
+unzip -u dist/Flipper-headless.zip -d /tmp
+(cd headless-tests && yarn test)