Nix installs stray bin/test-libstoreconsumer

[edolstra]

Describe the bug

This seems an unintended side-effect of #8517. @roberth

Steps To Reproduce

# nix build nix
# ls -l ./result/bin/
...
-r-xr-xr-x   2 root root   41984 Jan  1  1970 test-libstoreconsumer

Expected behavior

Don't install test-related artifacts.

nix-env --version output

Additional context

Add any other context about the problem here.

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