Use tbb@2020_u3 instead of tbb@2020

[scpeters]

The tbb@2020 formula in homebrew-core is deprecated, so use tbb@2020_u3 from our tap instead.

Testing: https://build.osrfoundation.org/job/gazebo-ci-gazebo11-homebrew-amd64/65/

This is a follow-up to #465.

[scpeters]

Testing: https://build.osrfoundation.org/job/gazebo-ci-gazebo11-homebrew-amd64/65/

The homebrew builds run make install, then brew doctor, then make tests. Previous tests (like this one succeeded at make install but failed brew doctor). The test listed above passed brew doctor but failed to link some tests with an undefined symbol:

Undefined symbols for architecture x86_64:
  "tbb::task::note_affinity(unsigned short)", referenced from:
      vtable for gazebo::transport::PublishTask in transport.cc.o
  "tbb::internal::allocate_root_proxy::free(tbb::task&)", referenced from:
      void gazebo::transport::Node::Publish<gazebo::msgs::Scene>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, google::protobuf::Message const&) in transport.cc.o
  "tbb::internal::allocate_root_proxy::allocate(unsigned long)", referenced from:
      void gazebo::transport::Node::Publish<gazebo::msgs::Scene>(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, google::protobuf::Message const&) in transport.cc.o
  "typeinfo for tbb::task", referenced from:
      typeinfo for gazebo::transport::PublishTask in transport.cc.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[3]: *** [test/integration/INTEGRATION_transport] Error 1

I'll test it locally to see if setting the LIBRARY_PATH will be enough to fix it

[scpeters]

I first tried setting CMAKE_PREFIX_PATH to include /usr/local/opt/tbb@2020_u3, but this is confounded by the fact that ogre1.9 depends on tbb:

https://github.com/osrf/homebrew-simulation/blob/76495dad046bcc7f006e0d94be66b9d4fd9c9914/Formula/ogre1.9.rb#L24

and in my first tests it appears to be getting the tbb headers from a -I/usr/local/include compiler argument

I'll see if I can just set CPATH and LIBRARY_PATH instead

[scpeters]

I've set CMAKE_PREFIX_PATH and LIBRARY_PATH as well in 742112d

https://build.osrfoundation.org/job/gazebo-ci-gazebo11-homebrew-amd64/66/

https://build.osrfoundation.org/job/gazebo-ci-gazebo11-homebrew-amd64/67/

[scpeters]

it's working now

[scpeters]

merging without review in order to fix gazebo CI