Make Random::setSeedRandomly() globalSeed atomic to fix a data race when multiple threads create a Random object

modules/juce_core/maths/juce_Random.cpp

@@ -58,7 +58,7 @@ void Random::combineSeed (const int64 seedValue) noexcept
 
 void Random::setSeedRandomly()
 {
-    static int64 globalSeed = 0;
+    static std::atomic<int64> globalSeed { 0 };
 
     combineSeed (globalSeed ^ (int64) (pointer_sized_int) this);
     combineSeed (Time::getMillisecondCounter());