Update the EBO static_assert to dheck against APFloat::Storage instead of IEEEFloat.

Author: DanielCChen

llvm/include/llvm/ADT/APFloat.h

@@ -1474,10 +1474,14 @@ class APFloat : public APFloatBase {
   friend APFloat frexp(const APFloat &X, int &Exp, roundingMode RM);
   friend IEEEFloat;
   friend DoubleAPFloat;
+  friend class APFloatEBOChecker;
+};
+
+class APFloatEBOChecker {
+  static_assert(sizeof(APFloat) == sizeof(APFloat::U),
+                "Empty base class optimization is not performed.");
 };
 
-static_assert(sizeof(APFloat) == sizeof(detail::IEEEFloat),
-              "Empty base class optimization is not performed.");
 
 /// See friend declarations above.
 ///