[flang-commits] [flang] [flang][driver] Improve diagnostic for assembly inputs (PR #174316)

[Tarun Prabhu via flang-commits]

tarunprabhu wrote:

> NOTE: This is not a strong opinion. The current implementation still looks good to me.

@yus3710-fj, Thanks for pointing out `Driver::BuildInputs` as the location for this code. It is definitely a better location for this check. 

However, would you be ok with leaving the implementation in `flang-driver/` as it currently is? This way, the change is contained within flang. Moving the code to `Driver::BuildInputs` would require the clang maintainers approval as well. Since we would like to support assembling with flang's driver at some point, we can avoid the churn of later moving that code out of the shared driver in the future.

The caveat here is that I am not sure how much effort would be needed to build an assembler for flang (`fc1as` analogous to `cc1as`) - so it may well be that we don't support assembling for some time.

https://github.com/llvm/llvm-project/pull/174316