[llvm] [LLVM] Create `lf_alias` nodes for `typedef` and `using` (PR #153936)

[via llvm-commits]

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@@ -1728,14 +1728,17 @@ TypeIndex CodeViewDebug::lowerTypeAlias(const DIDerivedType *Ty) {
 
   addToUDTs(Ty);
 
+  AliasRecord AR(UnderlyingTypeIndex, TypeName);
+  auto alias_index = TypeTable.writeLeafType(AR);
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Walnut356 wrote:

Should be taken care of now. I used llvm-ir and `llc` since the .ll file ended up being about 3-4x smaller than the equivalent .asm (3kb vs 14kb) The additional checks ensure:

* `LF_ALIAS` is generated and references the correct underlying type
* variables reference the `LF_ALIAS` type instead of the underlying type
* the `S_UDT` node still exists and points to the `LF_ALIAS` node

https://github.com/llvm/llvm-project/pull/153936