Quick Start for config does not mention CONFIG_MODVERSIONS=n dependency

[futuretim]

I will make a pull request for this but wanted to document it. The quickstart guide does not mention that the Rust options in menuconfig won't show up if you happen to have CONFIG_MODVERSIONS=y from an old config. Just user error; but for newbies (:raised_hands: ) it can be confusing and someone with even less experience wouldn't even know how to track this down.

[phideg]

Today I ran through the quick-start.rst myself (absolute beginner). I ran into a similar issue. I figured that I needed to first switch off DEBUG_INFO_BTF in my .config file before running oldconfig.

...
# CONFIG_DEBUG_INFO_BTF is not set
...

Afterwards running make LLVM=1 oldconfig provided me the option to switch on RUST.

Also I thought that having success with the rustavailable target would allow me to see the Rust support entry with menuconfig.

Maybe it would be a good hint in the quick-start to check the list of depend on entries in init/Kconfig:

config RUST
	bool "Rust support"
	depends on HAVE_RUST
	depends on RUST_IS_AVAILABLE
	depends on !MODVERSIONS
	depends on !GCC_PLUGINS
	depends on !RANDSTRUCT
	depends on !DEBUG_INFO_BTF