[llvm] [flang][runtime] Refine state associated with child I/O (PR #150461)

[via llvm-commits]

ronlieb wrote:

small reproducer, requires an openmpi compiler invocation, so some kind of interaction
$ cat goo.f90
                dt =1.0
                write(*,*) 'dt: ',dt
               end
$ OMPI_FC=/COD/2025-07-26/trunk/bin/flang   /opt/openmpi-5.0.6-flang-new/bin/mpif90 -O2 goo.f90 -g
$ ./a.out
     dt:  1.
Segmentation fault (core dumped)


https://github.com/llvm/llvm-project/pull/150461