bazel: fix build in G3
bazel: fix build in G3

Because we have the third_party/perfetto prefix in G3, we need to also
add this prefix when setting the root.

Change-Id: I4dbaf9c5d132a47a7c53bda7ec8aaaa3e182eb47
google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto