set the qlogged quic-go version when building the interop runner image

qlog/qlog.go

@@ -18,9 +18,15 @@ import (
 	"github.com/francoispqt/gojay"
 )
 
+// Setting of this only works when quic-go is used as a library.
+// When building a binary from this repository, the version can be set using the following go build flag:
+// -ldflags="-X github.com/lucas-clemente/quic-go/qlog.quicGoVersion=foobar"
 var quicGoVersion = "(devel)"
 
 func init() {
+	if quicGoVersion != "(devel)" { // variable set by ldflags
+		return
+	}
 	info, ok := debug.ReadBuildInfo()
 	if !ok { // no build info available. This happens when quic-go is not used as a library.
 		return
@@ -29,7 +35,11 @@ func init() {
 		if d.Path == "github.com/lucas-clemente/quic-go" {
 			quicGoVersion = d.Version
 			if d.Replace != nil {
-				quicGoVersion += " (replaced)"
+				if len(d.Replace.Version) > 0 {
+					quicGoVersion = d.Version
+				} else {
+					quicGoVersion += " (replaced)"
+				}
 			}
 			break
 		}