fix(corpus-sweep): name every missing required flag, in flag order

cmd/internal-tools/corpus-sweep/main.go

@@ -154,16 +154,28 @@ func parseArguments(arguments []string, stderr io.Writer) (config, error) {
 	}
 	configuration.extraArguments = flagSet.Args()
 
-	for name, value := range map[string]string{
-		"--corpus": configuration.corpusRoot,
-		"--spec":   configuration.specPath,
-		"--seeds":  seedSpecification,
-		"--output": configuration.outputDirectory,
+	// Every missing flag is named together, in flag order: stopping at the
+	// first turns one rerun into one rerun per missing flag.
+	var missing []error
+	for _, required := range []struct {
+		name  string
+		value string
+	}{
+		{"--corpus", configuration.corpusRoot},
+		{"--spec", configuration.specPath},
+		{"--seeds", seedSpecification},
+		{"--output", configuration.outputDirectory},
 	} {
-		if value == "" {
-			return config{}, fmt.Errorf("%s is required", name)
+		if required.value == "" {
+			missing = append(
+				missing,
+				fmt.Errorf("%s is required", required.name),
+			)
 		}
 	}
+	if err := errors.Join(missing...); err != nil {
+		return config{}, err
+	}
 	if configuration.maxSteps <= 0 {
 		return config{}, fmt.Errorf(
 			"--max-steps must be positive: every implementation needs the same step budget",