Fix errors from local testnet scripts on MacOS (#2919)

## Issue Addressed

Resolves https://github.com/sigp/lighthouse/issues/2763

## Proposed Changes

- Add a workflow which tests that local testnet starts successfully
  - Added `set` option into the scripts in order to fail fast so that we can notice errors during starting local testnet.
- Fix errors on MacOS
  - The redirect `&>>` is supported since bash v4 but the version bundled in macOS(11.6.1) is v3. a54f119c9b

scripts/local_testnet/print_logs.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+# Print the tail of all the logs output from local testnet
+
+set -Eeuo pipefail
+
+source ./vars.env
+
+for f in "$TESTNET_DIR"/*.log
+do
+  [[ -e "$f" ]] || break # handle the case of no *.log files
+  echo "============================================================================="
+  echo "$f"
+  echo "============================================================================="
+  tail "$f"
+  echo ""
+done