Hi guix,

This patch series adds a #:sh keyword argument to wrap-qt-program
and adjusts callers to set this keyword argument appropriately.

Setting this argument appropriately is required for cross-compilation.
Otherwise, a bash for SYSTEM (as in --system=..) is used instead
of a bash for TARGET (as in --target=...).

I didn't test building some qt programs with this patch series yet,
as I'm currently waiting on the substitute servers to catch up
with recent changed to core-updates (to avoid building a tower
of rusts). I'll do that later.

Greetings,
Maxime