package/python3: add patch to fix highly parallel builds

package/python3: add patch to fix highly parallel builds

Highly parallel host-python3 builds sometimes fail with:

Exception in thread Thread-1:
Traceback (most recent call last):
  File "/tmp/instance-3/output-1/host/lib/python3.9/threading.py", line 973, in _bootstrap_inner
    self.run()
  File "/tmp/instance-3/output-1/host/lib/python3.9/concurrent/futures/process.py", line 317, in run
    result_item, is_broken, cause = self.wait_result_broken_or_wakeup()
  File "/tmp/instance-3/output-1/host/lib/python3.9/concurrent/futures/process.py", line 376, in wait_result_broken_or_wakeup
    worker_sentinels = [p.sentinel for p in self.processes.values()]
  File "/tmp/instance-3/output-1/host/lib/python3.9/concurrent/futures/process.py", line 376, in <listcomp>
    worker_sentinels = [p.sentinel for p in self.processes.values()]
RuntimeError: dictionary changed size during iteration

During the compile_all.py step of host-python3. This issue is reported
upstream at https://bugs.python.org/issue43498, and while not yet
fixed upstream, a PR was proposed with a possible fix for it. Seems
the PR seems reasonable, let's give it a chance and see if it improves
the situation.

Hopefully Fixes:

  http://autobuild.buildroot.net/results/ae6c4ab292589a4e4442dfb0a1286349a9bf4d29/

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>