libutil: add util_exit_code

zdev uses a particular set of exit codes -- In preparation for sharing
some zdev udev code with other libraries, let's also create a libutil
include to specify reusable exit codes.  For now, let's just initialize
it with the codes from zdev we care about.

Reviewed-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
Reviewed-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

include/lib/util_exit_code.h

@@ -0,0 +1,21 @@
+/**
+ * @defgroup util_exit_code_h util_exit_code: General purpose exit codes
+ * @{
+ * @brief General purpose exit codes
+ *
+ * Copyright IBM Corp. 2022
+ *
+ * s390-tools is free software; you can redistribute it and/or modify
+ * it under the terms of the MIT license. See LICENSE for details.
+ */
+
+#ifndef LIB_UTIL_EXIT_CODE_H
+#define LIB_UTIL_EXIT_CODE_H
+
+typedef enum {
+	UTIL_EXIT_OK		= 0,  /* Program finished successfully */
+	UTIL_EXIT_RUNTIME_ERROR	= 15, /* A run-time error occurred */
+	UTIL_EXIT_OUT_OF_MEMORY	= 22, /* Not enough available memory */
+} util_exit_code_t;
+
+#endif /** LIB_UTIL_EXIT_CODE_H @} */