[flang][WIP] Refactor ISO_FORTRAN_ENV to move kind arrays to global symbols

[mjklemm]

This PR resolves issue #89403 by turning the constant implied-shape shape arrays for integer-kinds, real-kinds, and logical_kinds into regular arrays. That way, they can be accessed using variable indexes.

[mjklemm]

This PR is one way to fix the mentioned bug. Not sure if code-gen could/should be adapted to solve this problem in the compiler itself.

One thing thing that I still need to figure out (help appreciated) is how to get the object file of the newly added module linked into FortranRuntime. It might be good to have a general way to do this in case there will be more modules that have an implementation part and thus cannot be translated using -fsyntax-only.

[klausler]

The REAL_KINDS exported from ISO_FORTRAN_ENV is not a named constant after this change, right? So it would no longer work in a constant expression or initializer. That seems like a non-starter, if so.

[mjklemm]

The REAL_KINDS exported from ISO_FORTRAN_ENV is not a named constant after this change, right? So it would no longer work in a constant expression or initializer. That seems like a non-starter, if so.

Hm... You're right. So, this needs to go back to the drawing board... So, this needs to be fixed in code-gen, I guess.

[klausler]

The REAL_KINDS exported from ISO_FORTRAN_ENV is not a named constant after this change, right? So it would no longer work in a constant expression or initializer. That seems like a non-starter, if so.

Hm... You're right. So, this needs to go back to the drawing board... So, this needs to be fixed in code-gen, I guess.

Lowering doesn't seem like the right place, either. What's necessary is compiling the modules into relocatable object files and incorporating them into the runtime support library. The modules need to be compiled with target information in hand, anyway; their contents reflect the build host today.

[mjklemm]

The modules do not compile right now. For ISO_FORTRAN_ENV, actually compiling the module file resulted in the compiler choking about numeric_storage_size intrinsic not being implemented.

[mjklemm]

I'll drop this PR. Let's discuss the potential solution over in the issue. That seems more appropriate going forward.