closes bpo-32859: Don't retry dup3() if it is not available at runtime (GH-5708)

closes bpo-32859: Don't retry dup3() if it is not available at runtime (GH-5708)

os.dup2() tests for dup3() system call availability at runtime,
but doesn't remember the result across calls, repeating
the test on each call with inheritable=False.

Since the caller of os.dup2() is expected to hold the GIL,
fix this by making the variable holding the test result static.
(cherry picked from commit b3caf388a0418f6c031e4dbdcc0c1ce7e5cc36bd)

Co-authored-by: Alexey Izbyshev <izbyshev@users.noreply.github.com>