GCC Clang Pragma Warning Fix, 23.0 branch (2023.07.10.)

As it turns out (see !64172 (comment 6900052) and https://bigpanda.cern.ch/nview/?nightly=main--dev4LCG_Athena_x86_64-el9-gcc13-opt), GCC is very touchy about seeing pragmas that are not meant for it. So we need to only expose these pragmas to the ROOT dictionary generation. Even Clang as the main C++ compiler does not need to see them.

This is a follow-up to !64172 (merged). But I still don't know how I missed these while writing that MR.

Let's hope that this will be the end of this issue (ATLINFR-4996)... Pinging @christos and @elmsheus.

Control/AthContainers/AthContainers/tools/threading.h

@@ -133,14 +133,14 @@ private:
 
 // See ATLINFR-4996 for an explanation of this clunky
 // warning suppression.
-#if __cplusplus > 201703L
+#if (__cplusplus > 201703L) && defined(__ROOTCLING__)
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdeprecated-volatile"
-#endif  // >C++17
+#endif  // >C++17 with ROOT
 #include "tbb/concurrent_vector.h"
-#if __cplusplus > 201703L
+#if (__cplusplus > 201703L) && defined(__ROOTCLING__)
 #pragma clang diagnostic pop
-#endif  // >C++17
+#endif  // >C++17 with ROOT
 
 #include <atomic>
 #include <mutex>
@@ -191,7 +191,7 @@ namespace AthContainers_detail {
  * lock on the underlying object rather than an exclusive one.
  */
 template <typename LOCKABLE>
-class strict_shared_lock 
+class strict_shared_lock
 {
 public:
   /// The underlying object type.
@@ -210,7 +210,7 @@ public:
    * @param obj The lockable object.
    */
   explicit strict_shared_lock(const lockable_type& obj);
-  
+
 
   /**
    * @brief Release the held lock.