[flang][OpenMP][debug] runtime calls in a reducing worksharing construct are attributed to a line in a different subroutine

Consider the following testcase:

```fortran
subroutine first_user(a, s)
integer :: a, s, i
s = 0
!$omp parallel do reduction(+:s) ! line 4
do i = 1, 4
s = s + a
end do
!$omp end parallel do
end subroutine first_user

subroutine second_user(a, s)
integer :: a, s, i
s = 0
!$omp parallel do reduction(+:s) ! line 14
do i = 1, 4
s = s + a
end do
!$omp end parallel do
end subroutine second_user
```

```
flang -fopenmp -g -O0 -S -emit-llvm test.f90
```

Inside `second_user_..omp_par`, many runtime call reports line 4, which is `first_user`'s directive.