py3: replace `time.clock()` with `time.perf_counter()`
The former was removed in 3.8. The util function uses `time.clock()` if the
latter is unavailable.
Differential Revision: https://phab.mercurial-scm.org/D7779
BasedOnStyle: LLVM
IndentWidth: 8
UseTab: ForIndentation
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
AllowShortBlocksOnASingleLine: false
AllowShortFunctionsOnASingleLine: false
IncludeCategories:
- Regex: '^<'
Priority: 1
- Regex: '^"'
Priority: 2