Make use of '#pragma clang diagnostic' only with __clang__.

compiler-rt/lib/sanitizer_common/sanitizer_procmaps.h

 
 class MemoryMappingLayout : public MemoryMappingLayoutBase {
  public:
   explicit MemoryMappingLayout(bool cache_enabled);
 
 // This destructor cannot be virtual, as it would cause an operator new() linking
 // failures in hwasan test cases. However non-virtual destructors emit warnings
 // in macOS build, hence disabling those
+#ifdef __clang__
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wnon-virtual-dtor"
+#endif
   ~MemoryMappingLayout();
+#ifdef __clang__
 #pragma clang diagnostic pop
+#endif
 
   virtual bool Next(MemoryMappedSegment *segment) override;
   virtual bool Error() const override;
   virtual void Reset() override;
   // In some cases, e.g. when running under a sandbox on Linux, ASan is unable
   // to obtain the memory mappings. It should fall back to pre-cached data
   // instead of aborting.
   static void CacheMemoryMappings();