[flang-commits] [flang] [Flang] Use `LLVMConversionTarget` instead of `ConversionTarget`. (PR #169770)

[Tom Eccles via flang-commits]

https://github.com/tblah commented:

LLVMConversionTarget inherits from ConversionTarget. The constructor does
```
addLegalDialect<LLVM::LLVMDialect>();
addLegalOp<UnrealizedConversionCastOp>();
```

I'm not sure what the effects are of allowing unrealized conversion casts. Please could you explain this more in the PR description?

https://github.com/llvm/llvm-project/pull/169770