tests: Fix guix-package.sh.

GCC is now a hidden package, so cannot be installed.

* tests/guix-package.sh: Replace 'gcc' by 'zile' in a test that install
multiple packages.

tests/guix-package.sh

@@ -85,7 +85,7 @@ then false; else true; fi
 guix package -p "$profile" --delete-generations=0
 
 # Make sure multiple arguments to -i works.
-guix package --bootstrap -i guile gcc -p "$profile" -n
+guix package --bootstrap -i guile zile -p "$profile" -n
 
 # Make sure the `:' syntax works.
 guix package --bootstrap -i "glibc:debug" -p "$profile" -n