Update CI to run interoperability tests. (#561)
Motivation:
We don't run the interoperability tests in CI at the moment, we should
run them against a different implementation to help ensure we don't
regress.
Modifications:
- Add two additional CI jobs to run the interoperability tests (which do
not run the other tests).
- Update the Travis setup so the steps run are in .travis-script.sh
instead of inline in .travis.yml
- Update .travis-install to conditionally install Bazel from source and
build the gRPC C++ interop testing servers
- Update the Makefile to make it more configurable (i.e. 'swift' can be
set to make it easier to run with different toolchains via xcrun)
Result:
- Interop tests will be run in CI in separate build jobs
George Barnett