Set best practice bash flags on post-generate.sh script (#3305)

Addresses
#3297 (comment)

Author: shreyas-goenka

tools/post-generate.sh

@@ -1,3 +1,7 @@
+#!/bin/bash
+
+set -euxo pipefail
+
 # Ensure the SDK version is consistent with the OpenAPI SHA the CLI is generated from.
 go test -timeout 240s -run TestConsistentDatabricksSdkVersion github.com/databricks/cli/internal/build