install packages to a different root directory

We need to install packages to a directory other than `/usr/local`, because we need to be able to access multiple VFX reference platforms without having to switch between different Docker images.

The shell scripts that build each package allow you to specify any location you want, which is a good start. But adapting the Dockerfiles to build and install **all** the packages to a different location is a huge headache. (For me, anyway.)

Has anybody else out there been confronted with this problem? And perhaps found a solution?

Start by reviewing the shell scripts that build each package and the Dockerfiles that install them. Determine how installation paths are currently selected and what changes would be needed for one configurable root; done should mean all packages can be built and installed there so multiple VFX reference platforms can be accessed without switching Docker images.

Written by the indexing model from the issue text.