Port gen_compile_commands.py from Linux to U-Boot

[Joao Paulo Goncalves]

>Hello U-Boot community,

>I'm submitting a patch series that ports the gen_compile_commands.py
>script from the Linux kernel's sources to U-Boot. This script, originally
>located in scripts/clang-tools/gen_compile_commands.py, enables the
>generation of compile_commands.json file for improved code navigation
>and analysis. The series consists of the initial script import, the
>necessary modifications for U-Boot compatibility, and finally some
>documentation.

Tested-by: Joao Paulo Goncalves <joao.goncalves at toradex.com>