BIND: Enable hermetic zone builds (#2275)

Co-authored-by: Tom Limoncelli <tal@whatexit.org>

providers/bind/serial.go

@@ -4,6 +4,8 @@ import (
 	"log"
 	"strconv"
 	"time"
+
+	"github.com/StackExchange/dnscontrol/v3/pkg/bindserial"
 )
 
 var nowFunc = time.Now
@@ -18,6 +20,12 @@ func generateSerial(oldSerial uint32) uint32 {
 	// that is smaller than the old one, we punt and increment the old number.
 	// At no time will a serial number == 0 be returned.
 
+	if bindserial.ForcedValue != 0 {
+		// https://github.com/StackExchange/dnscontrol/issues/1859
+		// User needs to have reproducible builds and BIND generates
+		return uint32(bindserial.ForcedValue & 0xFFFF)
+	}
+
 	original := oldSerial
 	var newSerial uint32