Test rust configuration and installation scripts

[lcampit]

The installation script for rust needs to be thoroughly tested to make sure it works both with or without an existing rust configuration, backing up existing configs or overwriting them

[lcampit]

As of now, cargo configuration does not allow for variables in paths. The cargo configuration installation script that tries to point to sccache executable in $CARGO_HOME does not work. A different path definition method must be used to ensure script does not contain hardcoded values