linuxPackages: 6.6 -> 6.12 (#370410)

  Users on old macOS versions should consider upgrading to a supported version (potentially using [OpenCore Legacy Patcher](https://dortania.github.io/OpenCore-Legacy-Patcher/) for old hardware) or installing NixOS.

  If neither of those options are viable and you require new versions of software, [MacPorts](https://www.macports.org/) supports versions back to Mac OS X Snow Leopard 10.6.

- The default kernel package has been updated from 6.6 to 6.12. All supported kernels remain available.

- GCC has been updated from GCC 13 to GCC 14.

  This introduces some backwards‐incompatible changes; see the [upstream porting guide](https://gcc.gnu.org/gcc-14/porting_to.html) for details.

  });

  packageAliases = {

    linux_default = packages.linux_6_6;

    linux_default = packages.linux_6_12;

    # Update this when adding the newest kernel major version!

    linux_latest = packages.linux_6_12;

    linux_rt_default = packages.linux_rt_5_15;