tools/nolibc/stdlib: implement abort()

libgcc uses it for certain divide functions, so it must be exported. Like
for memset() we do that in its own section so that the linker can strip
it when not needed.
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

tools/include/nolibc/stdlib.h

@@ -23,6 +23,14 @@ static __attribute__((unused)) char itoa_buffer[21];
  * As much as possible, please keep functions alphabetically sorted.
  */
 
+/* must be exported, as it's used by libgcc for various divide functions */
+__attribute__((weak,unused,noreturn,section(".text.nolibc_abort")))
+void abort(void)
+{
+	sys_kill(sys_getpid(), SIGABRT);
+	for (;;);
+}
+
 static __attribute__((unused))
 long atol(const char *s)
 {