add .ji extension so inputs to samefile both exist

Correct .rst on sysimg

Added needed newline.
(cherry picked from commit a16981d)

Conflicts:
	doc/devdocs/sysimg.rst

contrib/build_sysimg.jl

@@ -62,7 +62,7 @@ function build_sysimg(sysimg_path=default_sysimg_path, cpu_target="native", user
                 info("System image successfully built at $sysimg_path.ji")
             end
 
-            if !Base.samefile(default_sysimg_path, sysimg_path)
+            if !Base.samefile("$default_sysimg_path.ji", "$sysimg_path.ji")
                 info("To run Julia with this image loaded, run: julia -J $sysimg_path.ji")
             else
                 info("Julia will automatically load this system image at next startup")

doc/devdocs/sysimg.rst

@@ -23,8 +23,8 @@ Julia now ships with a script that automates the tasks of building the system im
 This will include a ``build_sysimg()`` function:
 
 .. function:: build_sysimg(sysimg_path=default_sysimg_path, cpu_target="native", userimg_path=nothing; force=false)
-   Rebuild the system image.
-   Store it in ``sysimg_path``, which defaults to a file named ``sys.ji`` that sits in the same folder as ``libjulia.{so,dylib}``, except on Windows where it defaults to ``JULIA_HOME/../lib/julia/sys.ji``.
+
+   Rebuild the system image. Store it in ``sysimg_path``, which defaults to a file named ``sys.ji`` that sits in the same folder as ``libjulia.{so,dylib}``, except on Windows where it defaults to ``JULIA_HOME/../lib/julia/sys.ji``.
    Use the cpu instruction set given by ``cpu_target``.  Valid CPU targets are the same as for the ``-C`` option to ``julia``, or the ``-march`` option to ``gcc``.  Defaults to ``native``, which means to use all CPU instructions available on the current processor.
    Include the user image file given by ``userimg_path``, which should contain directives such as ``using MyPackage`` to include that package in the new system image.
    New system image will not replace an older image unless ``force`` is set to true.