Auto merge of #106673 - flba-eb:add_qnx_nto_stdlib, r=workingjubilee

Add support for QNX Neutrino to standard library

This change:

- adds standard library support for QNX Neutrino (7.1).
- upgrades `libc` to version `0.2.139` which supports QNX Neutrino

`@gh-tr`

⚠️ Backtraces on QNX require rust-lang/backtrace-rs#507 which is not yet merged! (But everything else works without these changes) ⚠️

Tested mainly with a x86_64 virtual machine (see qnx-nto.md) and partially with an aarch64 hardware (some tests fail due to constrained resources).

Author: bors