genscripts comment tidy

[Nick Alcock]

On 16 Oct 2019, Alan Modra spake thusly:

> -# A .x script file is the default script.
> -# A .xr script is for linking without relocation (-r flag).
> -# A .xu script is like .xr, but *do* create constructors (-Ur flag).
> -# A .xn script is for linking with -n flag (mix text and data on same page).
> -# A .xbn script is for linking with -N flag (mix text and data on same page).
> -# A .xs script is for generating a shared library with the --shared
> -#   flag; it is only generated if $GENERATE_SHLIB_SCRIPT is set by the
> -#   emulation parameters.
> -# A .xc script is for linking with -z combreloc; it is only generated if
> -#   $GENERATE_COMBRELOC_SCRIPT is set by the emulation parameters or
> -#   $SCRIPT_NAME is "elf".
> -# A .xsc script is for linking with --shared -z combreloc; it is generated
> -#   if $GENERATE_COMBRELOC_SCRIPT is set by the emulation parameters or
> -#   $SCRIPT_NAME is "elf" and $GENERATE_SHLIB_SCRIPT is set by the emulation
> -#   parameters too.

Is this stuff still documented anywhere after this commit? Because I
know I found this specific comment very useful only a month ago, and the
purpose of the differently suffixed linker scripts is otherwise quite opaque.