bug#53790: Audacity has extraneous binary at directory root

[Leo Famulari]

Our Audacity package creates an extraneous "audacity" binary in the root
of the store item:

------
$ git describe                                   
v1.3.0-15695-gba60aede97 
$ ls -la $(./pre-inst-env guix build audacity)    
total 49012                
dr-xr-xr-x    6 root root          4096 Dec 31  1969 .
drwxrwxr-t 3440 root guixbuild 50139136 Feb  4 17:00 ..
-r-xr-xr-x    1 root root           337 Dec 31  1969 audacity
dr-xr-xr-x    2 root root          4096 Dec 31  1969 bin
dr-xr-xr-x    2 root root          4096 Dec 31  1969 etc
dr-xr-xr-x    3 root root          4096 Dec 31  1969 lib
dr-xr-xr-x   11 root root          4096 Dec 31  1969 share
$ ls -la $(./pre-inst-env guix build audacity)/bin
total 18404
dr-xr-xr-x 2 root root     4096 Dec 31  1969 .
dr-xr-xr-x 6 root root     4096 Dec 31  1969 ..
-r-xr-xr-x 1 root root      600 Dec 31  1969 audacity
-r-xr-xr-x 2 root root 18827912 Dec 31  1969 .audacity-real
------

This didn't occur before the update from Audacity 2.4.2 to 3.1.3.