Add license file for tools/valgrind/asan/third_party

Bug: 365320983
Change-Id: I8d4b1fc42e28cc6496c6220868326941855ef66c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5847348
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1353478}
NOKEYCHECK=True
GitOrigin-RevId: e5c8ea631a8d3ff802f3ba609ad8cb6ccd7a97ad