Updating commands for non windows machines

@pranavkm 

With these changes I was able to get to the point where MusicStore tests start to run. I need to check it on CI Linux machines to be make sure though
`exec program='cmd' commandline='/C ${npmCmd} ${npmCommand}' workingdir='${npmDir} if='!IsLinux'`
`exec program='${npmCmd}' commandline='${npmCommand}' workingdir='${npmDir} if='IsLinux'`