sched/assert: Call abort() instead of exit() in assert

POSIX dictates that assert() terminates via abort(), even though in NuttX
abort() just calls exit(EXIT_FAILURE) it is better to use the correct
API here, if at some point a proper implementation for abort() is made.

Also, as the kernel must not use abort() which is a userspace API, direct
the exit to PANIC() if for some reason _assert() returns (it should not
but trap it here just in case).

libs/libc/assert/lib_assert.c

@@ -27,6 +27,16 @@
 #include <assert.h>
 #include <stdlib.h>
 
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+/* If assert() is called from kernel, must not call user API abort */
+
+#ifdef __KERNEL__
+#  define abort PANIC
+#endif
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -34,5 +44,5 @@
 void __assert(FAR const char *filename, int linenum, FAR const char *msg)
 {
   _assert(filename, linenum, msg);
-  exit(EXIT_FAILURE);
+  abort();
 }