Fix pedanic warnings without a storage increase

Use RTEMS_ZERO_LENGTH_ARRAY for flexible array member.

Update #4662.

cpukit/include/rtems/confdefs/scheduler.h

@@ -234,7 +234,17 @@ extern "C" {
 #endif
 
 #ifdef CONFIGURE_SCHEDULER
+  /*
+   * Ignore these warnings:
+   *
+   * - invalid use of structure with flexible array member
+   *
+   * - struct has no members
+   */
+  #pragma GCC diagnostic push
+  #pragma GCC diagnostic ignored "-Wpedantic"
   CONFIGURE_SCHEDULER;
+  #pragma GCC diagnostic pop
 #endif
 
 const Scheduler_Control _Scheduler_Table[] = {

cpukit/include/rtems/score/schedulerpriority.h

@@ -94,7 +94,7 @@ typedef struct {
   /**
    * @brief One ready queue per priority level.
    */
-  Chain_Control Ready[ 1 ];
+  Chain_Control Ready[ RTEMS_ZERO_LENGTH_ARRAY ];
 } Scheduler_priority_Context;
 
 /**