`python3` fails at runtime with `newlib` and `pthread-embedded`

[mariasfiraiala]

As @eduardvintila's work regarding newlib and pthread-embedded compatibility with the new code base gets upstreamed, python3 fails at runtime with:

Booting from ROM..Powered by
o.   .o       _ _               __ _
Oo   Oo  ___ (_) | __ __  __ _ ' _) :_
oO   oO ' _ `| | |/ /  _)' _` | |_|  _)
oOo oOO| | | | |   (| | | (_) |  _) :_
 OoOoO ._, ._:_:_,\_._,  .__,_:_, \___)
      Epimetheus 0.12.0~51860332-custom
Fatal Python error: initfsencoding: unable to load the file system codec
ModuleNotFoundError: No module named 'encodings'

Current thread 0x000000003ff92020 (most recent call first):

This issue shall stay open as a reminder to fix whatever goes wrong here.