[clang] [CIR] Mark bit-field access units as their own member kinds (PR #216864)

[Erich Keane via cfe-commits]

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@@ -148,10 +148,18 @@ struct CIRRecordLowering final {
     return cirGenTypes.isZeroInitializable(rd);
   }
 
+  static cir::RecordMemberKind makeMemberKind(bool holdsData, bool isUnit) {
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erichkeane wrote:

what is a 'unit' here? 

https://github.com/llvm/llvm-project/pull/216864