tests: use `go test -a` to work around Go caching
tests: use `go test -a` to work around Go caching

Go does not notice when the C code changes, so we have to
use `go test -a`.

Workaround for https://github.com/golang/go/issues/24355 .

rfjakob/earlyoom,rfjakob/earlyoom,rfjakob/earlyoom,rfjakob/earlyoom