[flang-commits] [flang] [flang][Evaluate] Add `ExtractSubstring` to evaluate/tools.h (PR #81265)

[Krzysztof Parzyszek via flang-commits]

kparzysz wrote:

I'll be putting up a PR stack soon that uses this.  I'll include this in in there.  If this gets merged before then, it will have no impact, but it won't have its own separate commit anymore.

https://github.com/llvm/llvm-project/pull/81265