Fixed a compiler error in the DSP module when using clang C++17 support

modules/juce_dsp/processors/juce_WaveShaper.h

@@ -72,12 +72,14 @@ struct WaveShaper
 };
 
 //==============================================================================
-#if JUCE_CXX17_IS_AVAILABLE
+// Although clang supports C++17, their standard library still has no invoke_result
+// support. Remove the "|| JUCE_CLANG" once clang supports this properly!
+#if (! JUCE_CXX17_IS_AVAILABLE) || JUCE_CLANG
 template <typename Functor>
-static WaveShaper<typename std::invoke_result<Functor>, Functor> CreateWaveShaper (Functor functionToUse)   { return {functionToUse}; }
+static WaveShaper<typename std::result_of<Functor>, Functor> CreateWaveShaper (Functor functionToUse)   { return {functionToUse}; }
 #else
 template <typename Functor>
-static WaveShaper<typename std::result_of<Functor>, Functor> CreateWaveShaper (Functor functionToUse)   { return {functionToUse}; }
+static WaveShaper<typename std::invoke_result<Functor>, Functor> CreateWaveShaper (Functor functionToUse)   { return {functionToUse}; }
 #endif
 
 } // namespace dsp