Have run_code_generation only call vpython when needed gen_builtin_symbols.py uses a vpython module to generate a perfect hash function Also seeded the perfect hash function to make it deterministic Bug: angleproject:3747 Change-Id: I660fe71bd6b2213be9d4ccc2f68641637a49a047 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1738747 Commit-Queue: Clemen Deng <clemendeng@google.com> Reviewed-by: Geoff Lang <geofflang@chromium.org>