Fixes https://github.com/llvm/llvm-project/issues/113191
Issue: [flang][OpenMP] Runtime segfault when an allocatable variable is
used with copyin
Rootcause: The value of the threadprivate variable is not being copied
from the primary thread to the other threads within a parallel region.
As a result it tries to access a null pointer inside a parallel region
which causes segfault.
Fix: When allocatables used with copyin clause need to ensure that, on
entry to any parallel region each thread’s copy of a variable will
acquire the allocation status of the primary thread, before copying the
value of a threadprivate variable of the primary thread to the
threadprivate variable of each other member of the team.