Increase flexibility in IPPL build scripts
This MR adds customization of build options via environment variables and prevents the scripts for IPPL from overwriting build directories when the targets change. This is useful in environments where one works with several build directories.
In addition, an all-in-one wrapper script is provided. Currently, it only builds IPPL and its dependencies. The intention is for this script to provide a basis for a user-friendly install script that will install all relevant components with the correct configuration.