qt-build-system: prefix or suffix env-variables in wrap-program

[Hartmut Goebel <h.goebel@crazy-compilers.com>]

Hi,

it came to my mind that currently the qt-build-system wraps the program
without passing along any environment variables. Thus e.g.
XDG_CONFIG_DIRS will be overwritten, instead of not extended. Furtunatly
((guix build utils) wrap-program) supports prefixing or suffixing an
existing variable value.

Shall qt-build-system: prefix or suffix existing env-variables? Should
it become

    export
XDG_DATA_DIRS="$XDG_DATA_DIRS${XDG_DATA_DIRS:+:}/gnu/store/…-kate-…"

or

    export
XDG_DATA_DIRS="/gnu/store/…-kate-…${XDG_DATA_DIRS:+:}$XDG_DATA_DIRS"

Currently affected variables are:

XDG_DATA_DIRS
XDG_CONFIG_DIRS
QT_PLUGIN_PATH
QML_IMPORT_PATH

-- 
Regards
Hartmut Goebel

| Hartmut Goebel          | h.goebel@crazy-compilers.com               |
| www.crazy-compilers.com | compilers which you thought are impossible |