Travis-CI is dead. The new hotness if GitHub actions.
For now we only test on Linux since testing on macOS and Windows
takes more effort to figure out.
Change-Id: I464df75b9142dafcdf07281f70c1bcf52514f71a
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/298089
Trust: Joe Tsai <joetsai@digital-static.net>
Reviewed-by: Damien Neil <dneil@google.com>
