Add a tab in front of stack samples in report_sample.py

This brings the output closer to the output of linux-perf-tool script.

Some tools (e.g. FlameScope) optimise skipping lines starting with tabs, this should help those tools go faster.

BUG=200473657

Change-Id: I2144e4dbe83f82d14844082d5dedec14dc7f30fb
1 file changed