draft: qurt: Add support for Qualcomm QuRT

[androm3da]

The QuRT RTOS -- used primarily on the Hexagon architecture -- has support for large parts of POSIX.

Description

This change should add support for QuRT to libc.

Sources

This link: https://softwarecenter.qualcomm.com/api/download/software/sdks/Hexagon_SDK/Linux/Debian/6.3.0.0/Hexagon_SDK.zip contains the headers and archives/shared objects to be used with QuRT, e.g. /opt/Hexagon_SDK/6.3.0.0/rtos/qurt/computev69/include/{qurt,posix,qube}/ and /opt/Hexagon_SDK/6.3.0.0/rtos/qurt/computev69/lib.

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

I struggled to test this one - maybe I have something wrong with my configuration, I will re-check it.

[androm3da]

I'll close this for now and revisit it after rust-lang/rust#147173 lands.