Add a utility to parse output from llvm-bolt-wrapper script and
detect individual and aggregate time/memory swings. The wrapper reports
wall time and peak RSS for each BOLT invocation.
Exit code:
The utility exits with non-zero exit code if any individual test has
time or memory swing larger than `threshold_single` (default 10%), or
the aggregate (geometric mean) swing larger than `threshold_agg`
(default 5%). Short tests where BOLT wall time is less than
`check_longer_than` seconds (default 0.5s) are excluded from threshold
calculation.
Output:
The script prints test results exceeding the individual threshold, and
geomean values if it exceeds aggregate results. In `--verbose` mode all
individual results are printed (short time results are marked with '?').
Example usage:
```
$ cd ~/llvm-build # build folder where NFC testing was invoked
$ python3 ~/llvm-project/bolt/utils/nfc-stat-parser.py \
--check_longer_than 0.1 `find -name timing.log`
./tools/bolt/test/runtime/X86/exceptions-pic.test/ -88.46% -0.13%
Geomean -19.78% +0.37%
$ echo $?
1
```
