[dub] How to specify with dub a custom repository and build directory ?

[bioinfornatics]

Dear,

As 99% of d project use dub as build and package manager. I would 
like to know how to use D libraries and D software shared to all 
user on linux architecture ?

When I run:

  dub fetch <package name>

A .dub directory is created into $HOME. I tried to provide 
another directory with --root parameter but that do not work.

Currently I do not see how to build and install various D 
software at my works (HPC environment).

To be able to use D in this environment I need to be able to set 
at least:
- BUILD_DIR directory to perform build stage
- DESTDIR directory to tell where the root "start", it is useful 
for staged build such as rpm do
- PREFIX directory which will contains bin, include, lib(64), 
share directories
- use installed D library by reading env var LIBRARY_PATH, PATH, 
CPATH


Any highlight is welcome

Thanks