Rollup merge of #70392 - brain0:fixxpy, r=Mark-Simulacrum
Rollup merge of #70392 - brain0:fixxpy, r=Mark-Simulacrum

Make x.py compatible with python 3.8.

Python 3.8 removes the `time.clock()` function, use `time.perf_counter()` instead.

aidancully/rust,graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust