Add Environment Variables documentation to the book

[satk0]

It aims to resolve the rizin issue rizinorg/rizin#4445, but its NOT yet ready to merge !

While trying to solve it, I've met 2 problems:

• I don't know where to put rizin env vars doc (in a 16. Build Variables or create a new chapter?)
• rz-test is not documented, so nowhere to put env var doc (should I also document rz-test?)

[wargio]

Yes add a new section called Run-Time Variables after the Build Variables and probably we could rename Build Variables to Compile-Time Variables

[wargio]

@XVilka @kazarmy what do you think?

[wargio]

Regarding rz-test, it's not mapped in the book, because it is supposed to not be used by a user. its usage is available on the rizin repo itself: https://github.com/rizinorg/rizin/tree/dev/test#usage

[satk0]

Thanks for the answer. So I will just omit rz-test and focus on adding the new section and renaming Build Variables one.

[satk0]

Done, let me know how it looks

[wargio]

maybe use underscores instead of dashes for the files.

[wargio]

Suggested change

	After successful compilation, run-time variables will be exposed to change the default behavior of rizin.
	Run-time variables (also known as environment variables) can be used to change the default behavior when running rizin or tools.

[wargio]

Suggested change

	Description of these run-time variables can be accessed by executing the command `rizin -hh` on a terminal.
	The description of these run-time variables can be accessed by executing the command `rizin -hh` on a terminal.

[satk0]

Done, that's the whole list of env vars that you can print with -hh command.