Rollup merge of rust-lang#58544 - TheBiggerGuy:rustc-doc-cli-args, r=TimNN

Fix doc for rustc "-g" flag

The rustc `-g` CLI flag was miss documented to be a synonym of `-C debug-level=2` and not `-C debuglevel=2`. Also add links to the codegen docs for each synonym.

I am unsure of this will conflict with work on rust-lang#52938

Author: Mark-Simulacrum

src/doc/rustc/src/command-line-arguments.md

@@ -42,11 +42,11 @@ This flag prints out various information about the compiler.
 
 ## `-g`: include debug information
 
-A synonym for `-C debug-level=2`.
+A synonym for `-C debuginfo=2`, for more see [here](codegen-options/index.html#debuginfo).
 
 ## `-O`: optimize your code
 
-A synonym for `-C opt-level=2`.
+A synonym for `-C opt-level=2`, for more see [here](codegen-options/index.html#opt-level).
 
 ## `-o`: filename of the output