[bug#45081] [PATCH] gnu: stumpwm-with-slynk: Fix build error

[Niklas Eklund]

I encountered the following error trying to build stumpwm-with-slynk:

While evaluating the form starting at line 13, column 0
  of 
#P"/tmp/guix-build-stumpwm-with-slynk-20.11.drv-0/source/load-stumpwm.lisp":

debugger invoked on a SB-INT:SIMPLE-FILE-ERROR in thread
  Can't create directory /homeless-shelter/

I found a similar issue mentioned on the internet and tried the suggested
solution, which seems to work for me building in my development guix
environment.

If there is a better place to add this setenv form please feel free to make a
change to it :)

Cheers