[Flang] The maximum length of linked lists is shorter than other Fortran compilers

The maximum length of linked lists seems to be lower in Flang compared to other compilers (gfortran, ifx). Consider the following program:

```fortran
program main
implicit none
type t
real :: v
type(t), allocatable :: p
end type
call sub
print *, "pass"
contains
subroutine sub
implicit none
integer :: i
integer, parameter :: iter = 10000
type(t), target :: a
type(t), pointer :: head
head => a
head%v = 0
do i = 1,iter
allocate(head%p)
head => head%p
head%v = i
end do
end subroutine sub
end
```

The program execution terminates abnormally with Flang, but not with other compilers:
https://godbolt.org/z/KGro8je4T

If `iter` is 100000, other compilers also fail. If `iter` is 1000, Flang also succeeds.
https://godbolt.org/z/Krzc7s1Er

Start by compiling and running the linked-list reproducer with Flang, using the provided Compiler Explorer links to compare behavior with gfortran and ifx. Vary iter around 1,000, 10,000, and 100,000 to characterize the limit and identify whether the failure is in allocation, pointer handling, or runtime support. Done means the 10,000-node program completes normally without regressing the larger-case behavior.

Written by the indexing model from the issue text.