Add rule for proto file so we can write python to use it.

I wrote another tool filter and augment the proto files, but these proto
files need to have a python library for that tool.

Test: m filter_teams && out/host/linux-x86/bin/filter_teams  --filter_teams

Change-Id: I6b259ddda2b6c09d55a9c6d445b96e5b77741f09