ion/ionvcproj.py: adjusted pre-build event command to work for me

[travisstaloch]

The ion/ionvcproj.py script wasn't working for me. I made changes to the pre-build event which allow me to build and debug my ion code. The only thing I have to do now after running this script is 'retarget solution'.

You can see I added packagepathparent and ioncmd to the substitution variables. ioncmd assumes that the ion executable is named 'ion'.

    <PreBuildEvent>
      <Command>
        set IONHOME=$ionhome
        cd $packagepathparent 
        $ioncmd $flags $package
      </Command>
    </PreBuildEvent>

I believe my issues with the script were related to the VS terminal not picking up my IONHOME and also my perhaps nonstandard ion setup where I have an ion.bat in my path which points to %IONHOME%/ion.exe . This solution navigates instead to the directory above packagepath (rather than ionhome) and uses an absolute path to ion (ioncmd).