[llvm-branch-commits] [flang] [Flang][NFC] Split runtime headers in preparation for cross-compilation. (PR #112188)

[David Truby via llvm-branch-commits]

https://github.com/DavidTruby approved this pull request.

LGTM, but someone else should probably approve as this is quite a large change.
I don't think this one is an NFC because of the changes mentioned above by @jeanPerier 

https://github.com/llvm/llvm-project/pull/112188