Windows fixes for build_sysimg.jl from #9376

Windows fixes for sys.ji location and using .ji in messages instead of Sys.dlext

Fix WinRPM binutils location

change some messages from println() to info()

(cherry picked from commit cc9b2987202324b69d6430106db11b120ad9737e)

Refactor running the linker into a separate function

modify docs to reflect different paths on Windows

(cherry picked from commit a829806499360fffc64a21772114d44e76d8bff8)

Conflicts:
	doc/devdocs/sysimg.rst

use winrpm gcc instead of binutils to link sys.dll on windows

use Base.samefile for file path comparison

add instructions to Pkg.add("WinRPM") too

use -shared also on Windows, along with '-Wl,' only on Windows

(cherry picked from commit b7a5d801a8657ce0f458b3372b3ace96b5fa517d)

add .ji extension so inputs to samefile both exist
(cherry picked from commit 1506d309591838a8e3c04275696b273e73fa3e32)