chore: DRY linker scripts, picolibc & LLVM toolchain

[raphaelcoeffic]

Summary of changes:

• DRY linker scripts
• support for LLVM embedded toolchain including picolibc.

TODO:

• integrate Thread Local Storage init (see here).
• bump FreeRTOS and take advantage of TLS support added in 10.6.0.

[ajjjjjjjj]

Hi, does LLVM + picolibc give size or performance benefits?

[raphaelcoeffic]

Hi, does LLVM + picolibc give size or performance benefits?

It’s too early to say. The bootloader turns slightly smaller while the complete firmware is 1.5% bigger on average.

The main idea here is to be able to take advantage of LLVM’s static analyzers and better error messages.

picolibc seems to add a couple of interesting features:

• support for Thread Local Storage
• floating point string conversions that do not allocate memory in the process (newlib nano, just like the regular libc uses malloc when printing floating point numbers!)