[llvm] suppresses unused variable warning (PR #99526)

[David Blaikie via llvm-commits]

================
@@ -3361,7 +3361,7 @@ void InstrRefBasedLDV::buildVLocValueMap(
         continue;
       if (BlockLiveIn->Kind == DbgValue::VPHI)
         BlockLiveIn->Kind = DbgValue::Def;
-      auto &[Var, DILoc] = DVMap.lookupDVID(VarID);
+      [[maybe_unused]] auto &[Var, DILoc] = DVMap.lookupDVID(VarID);
----------------
dwblaikie wrote:

FWIW/next time, I'd consider rolling this into the assert, maybe?
```
      assert(BlockLiveIn->Properties.DIExpr->getFragmentInfo() ==
                 DVMap.lookupDVID(VarID).first.getFragment() &&
               ...
```
(so the optimizer doesn't have to deal with the lookup code in nonasserts builds)
(and/or if the named variable helped with readability/was needed for other reasons, maybe using `auto &VarID = ...(VarID).first;` ? rather than needing to name an extra fully unused variable (DILoc))

https://github.com/llvm/llvm-project/pull/99526