Update buildah to v1.11.0

Vendor in the latest changes for buildah to apply the implemented
features here as well.

Signed-off-by: Sascha Grunert <sgrunert@suse.com>

vendor/github.com/openshift/api/config/v1/stringsource.go

@@ -0,0 +1,31 @@
+package v1
+
+import "encoding/json"
+
+// UnmarshalJSON implements the json.Unmarshaller interface.
+// If the value is a string, it sets the Value field of the StringSource.
+// Otherwise, it is unmarshaled into the StringSourceSpec struct
+func (s *StringSource) UnmarshalJSON(value []byte) error {
+	// If we can unmarshal to a simple string, just set the value
+	var simpleValue string
+	if err := json.Unmarshal(value, &simpleValue); err == nil {
+		s.Value = simpleValue
+		return nil
+	}
+
+	// Otherwise do the full struct unmarshal
+	return json.Unmarshal(value, &s.StringSourceSpec)
+}
+
+// MarshalJSON implements the json.Marshaller interface.
+// If the StringSource contains only a string Value (or is empty), it is marshaled as a JSON string.
+// Otherwise, the StringSourceSpec struct is marshaled as a JSON object.
+func (s *StringSource) MarshalJSON() ([]byte, error) {
+	// If we have only a cleartext value set, do a simple string marshal
+	if s.StringSourceSpec == (StringSourceSpec{Value: s.Value}) {
+		return json.Marshal(s.Value)
+	}
+
+	// Otherwise do the full struct marshal of the externalized bits
+	return json.Marshal(s.StringSourceSpec)
+}