libc: minimal: Implement exit()/_exit() functions.

Behavior is similar to newlib version: print "exit" message and go
into infinite loop.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>

lib/libc/minimal/CMakeLists.txt

@@ -9,6 +9,7 @@ zephyr_library_sources(
   source/stdlib/strtoul.c
   source/stdlib/malloc.c
   source/stdlib/bsearch.c
+  source/stdlib/exit.c
   source/string/strncasecmp.c
   source/string/strstr.c
   source/string/string.c

lib/libc/minimal/include/stdlib.h

@@ -28,6 +28,14 @@ void *bsearch(const void *key, const void *array,
 	      size_t count, size_t size,
 	      int (*cmp)(const void *key, const void *element));
 
+#define EXIT_SUCCESS 0
+#define EXIT_FAILURE 1
+void _exit(int status);
+static inline void exit(int status)
+{
+	_exit(status);
+}
+
 int rand(void);
 
 #define abs(x) ((x) < 0 ? -(x) : (x))

lib/libc/minimal/source/stdlib/exit.c

@@ -0,0 +1,15 @@
+/*
+ * Copyright (c) 2019 Linaro Limited
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdlib.h>
+#include <zephyr.h>
+
+void _exit(int status)
+{
+	printk("exit\n");
+	while (1) {
+	}
+}