[clang] Fix Wnested-anon-types in ABIArgInfo

[teemperor]

Summary

D98794 added the DirectAttr/IndirectAttr struct fields to that union, but declaring anonymous structs in an anonymous union
triggers -Wnested-anon-types warnings. We can't just give them a name as they are in an anonymous union, so this just
declares the type outside.

clang/include/clang/CodeGen/CGFunctionInfo.h:97:5: warning: anonymous types declared in an anonymous union are an extension [-Wnested-anon-types]
    struct {
    ^
clang/include/clang/CodeGen/CGFunctionInfo.h:101:5: warning: anonymous types declared in an anonymous union are an extension [-Wnested-anon-types]
    struct {
    ^

[chill]

LGTM, cheers!

clang/include/clang/CodeGen/CGFunctionInfo.h

public:
   };
 
 private:
   llvm::Type *TypeData; // canHaveCoerceToType()
   union {
     llvm::Type *PaddingType; // canHavePaddingType()
     llvm::Type *UnpaddedCoerceAndExpandType; // isCoerceAndExpand()
   };
-  union {
-    struct {
-      unsigned Offset;
-      unsigned Align;
-    } DirectAttr;              // isDirect() || isExtend()
-    struct {
-      unsigned Align;
-      unsigned AddrSpace;
-    } IndirectAttr;            // isIndirect()
+  struct DirectAttrInfo {
+  };
+  struct IndirectAttrInfo {
+  };
+  union {
+    DirectAttrInfo DirectAttr;     // isDirect() || isExtend()
+    IndirectAttrInfo IndirectAttr; // isIndirect()
     unsigned AllocaFieldIndex; // isInAlloca()
   };
   Kind TheKind;
   bool PaddingInReg : 1;
   bool InAllocaSRet : 1;    // isInAlloca()
   bool InAllocaIndirect : 1;// isInAlloca()
   bool IndirectByVal : 1;   // isIndirect()
   bool IndirectRealign : 1; // isIndirect()