Hi priyanka tevare,
The Ridgerun SDK will look for the EZSDK install directory and create a tarball with the components needed, then if you have a packages directory like /opt/ridgerun/downloads it will save the tarball in that directory and continue using it in future builds if is needed, so it would be faster to build without downloading or creating tarballs again in future. If you don't have /opt/ridgerun/downloads, it will save it in $DEVDIR/downloads.
Now, in your case since you are using the eval SDK it doesn't support creating that tarball if you installed the EZSDK in /usr/local, try removing that one and installing it again in your /home/$USER directory. It will work.
Regards,
-David