Fix some Clang compile warnings

libs/JSystem/include/JSystem/J3DGraphBase/J3DMatBlock.h

@@ -116,7 +116,13 @@ public:
         // same logic but without the bug.
         // See J3DMaterialFactory::newColorChan - both the bugged and correct behavior are present there, as it calls
         // both constructors.
+#if TARGET_PC
+        // The faulty comparison is EXTREMELY noisy in the build due to warnings being emitted for
+        // every TU that includes it - best to just remove it since it doesn't do anything anyway.
+        u32 ambSrc = info.mAmbSrc;
+#else
         u32 ambSrc = info.mAmbSrc == 0xFFFF ? 0 : info.mAmbSrc;
+#endif
         mColorChanID = calcColorChanID(info.mEnable, info.mMatSrc, info.mLightMask,
             info.mDiffuseFn, info.mAttnFn, ambSrc);
     }

libs/JSystem/include/JSystem/JHostIO/JOREntry.h

@@ -99,7 +99,12 @@ public:
 
     static JHIComPortManager<T>* getInstance() { return instance; }
 
+#ifdef __MWERKS__
     static JHIComPortManager<T>* instance;
+#else
+    // C++17 allows in-class instantiation
+    static inline JHIComPortManager<T>* instance = nullptr;
+#endif
 
     /* 0x00000 */ T port;
     /* 0x0000C */ JHIpvector<JHITag<T>*, 10> field_0xc;