rpm/source_date_epoch_buildtime.diff

--- ./build/pack.c.orig	2018-03-27 12:21:03.036841297 +0000
+++ ./build/pack.c	2018-03-27 12:29:56.050400820 +0000
@@ -161,7 +161,7 @@ static rpm_time_t * getBuildTime(void)
 
     if (buildTime[0] == 0) {
         srcdate = getenv("SOURCE_DATE_EPOCH");
-        if (srcdate) {
+        if (srcdate && rpmExpandNumeric("%{?use_source_date_epoch_as_buildtime}")) {
             errno = 0;
             epoch = strtol(srcdate, &endptr, 10);
             if (srcdate == endptr || *endptr || errno != 0)