Set up some form of CI

[thomasvl]

Maybe https://swift.org/continuous-integration can be leveraged, but something should likely get set up to test things as they land and to test PRs as they come in.

[fabiomassimo]

Would a free solution for open source projects, like Travis, be a valid option for you?

[timburks]

+1 for Travis. The grpc-swift Travis tests recently failed with the following:

/home/travis/build/grpc/grpc-swift/Plugin/Packages/SwiftProtobuf-0.9.29/Sources/SwiftProtobuf/Google_Protobuf_Any+Registry.swift:50:31: error: use of unresolved identifier 'DispatchQueue'
fileprivate var serialQueue = DispatchQueue(label: "com.apple.swift.typeRegistry")

The problem appears to be that "import DispatchQueue" is only necessary on Linux. Since Travis tests run on Linux, it's likely that this would have been caught here.

EDIT: I see that the build failure was fixed in this commit.

[thomasvl]

#973 just added GitHub actions for a linux build.

[thomasvl]

Closing this since the linux CI actions are now running on PRs.