SOURCE_DATE_EPOCH: drop timezone

The timezone information is not exposed to the uint64 representation,
but exposed to RFC3339 representation.

Signed-off-by: Akihiro Suda <[email protected]>

Author: AkihiroSuda

exporter/util/epoch/parse.go

@@ -60,6 +60,6 @@ func parseTime(key, value string) (*time.Time, error) {
 	if err != nil {
 		return nil, errors.Wrapf(err, "invalid %s: %s", key, err)
 	}
-	tm := time.Unix(sde, 0)
+	tm := time.Unix(sde, 0).UTC()
 	return &tm, nil
 }

frontend/dockerfile/builder/build.go

@@ -1131,6 +1131,6 @@ func parseSourceDateEpoch(v string) (*time.Time, error) {
 	if err != nil {
 		return nil, errors.Wrapf(err, "invalid SOURCE_DATE_EPOCH: %s", v)
 	}
-	tm := time.Unix(sde, 0)
+	tm := time.Unix(sde, 0).UTC()
 	return &tm, nil
 }