tests: kernel: fix thread_runtime_stats compiler optimization issue

Compilers may optimize away empty while(1){} loops in helper threads,
causing the idle thread to run instead and breaking runtime statistics
measurement.

Use volatile condition variable to prevent optimization.

Signed-off-by: Mohamed Moawad <[email protected]>

Author: M-Moawad

tests/kernel/usage/thread_runtime_stats/src/test_thread_runtime_stats.c

@@ -33,7 +33,10 @@ static struct k_thread *main_thread;
  */
 void helper1(void *p1, void *p2, void *p3)
 {
-	while (1) {
+	/* Using volatile condition to prevent compilers from optimizing while(true) */
+	volatile bool condition = true;
+
+	while (condition) {
 	}
 }