When running an application using usertools/dpdk-setup.sh script, such as testpmd, the following command is executed "sudo $RTE_TARGET/app/testpmd". Where $RTE_TARGET is a variable, which is set when we compile dpdk using dpdk-setup script, otherwise it is empty. So lets say a person has pre-compiled dpdk and is just using the script to set hugepages and run testpmd, he would have to recompile just to set the variable. 

This issue can be resolved by asking the user to enter the name of his build directory if $RTE_TARGET is empty. The name entered by the user can then be stored in $RTE_TARGET.  

I can submit a patch if this solution seems appropriate.