Bump musl targets to musl 1.2.5 and GCC 14.3.0

Some of the existing musl targets in cross are still built with musl-cross-make using relatively old toolchain versions, currently around:

• musl 1.2.3
• GCC 9.2.0
• binutils 2.33.1

One practical issue with the current GCC version is its limited support for newer C/C++ standards, especially C++20. Some modern C/C++ dependencies now require newer compiler features, which can make them difficult or impossible to build with the existing musl images.

I am considering updating the older musl targets and would like to ask for maintainers' preference on two points:

1. Which versions should we target?

   Would musl 1.2.5 + GCC 14.2.0 be a reasonable baseline, matching the newer musl targets already used in cross?

   Alternatively, would you prefer a different GCC or musl version for compatibility reasons?

2. Should the existing musl targets continue using musl-cross-make, or should they be migrated to crosstool-ng?

   The current musl-cross-make based setup is relatively simple and already works for these targets, so updating the versions there would result in a smaller change.

   On the other hand, cross already uses crosstool-ng for several newer GNU and musl targets, so migrating the older musl targets could make toolchain configuration more consistent in the long term.

My current thought is either:

Option A:
keep musl-cross-make
musl 1.2.3 -> 1.2.5
GCC  9.2.0 -> 14.3.0

Before working on this, I would like to confirm which direction and version combination would be preferred.