Upgrade libtracefs to libtracefs-1.8.1

This project was upgraded with external_updater.
Usage: tools/external_updater/updater.sh update external/libtracefs
For more info, check https://cs.android.com/android/platform/superproject/main/+/main:tools/external_updater/README.md

Additionally: add -Wno-gnu, due to void pointer arithmetic complaints.
It's OK to use a GCC extension because we're building with -std=gnu99.

Bug: 393387208
Test: TreeHugger
Change-Id: I2b15547596690fa2f389ac591864631ae7226eb2