buildNoTests: Disable unit tests

This seems to have been the intent all along.

The odd combination of unit tests, but no functional tests caused a
build error where some data for the unit test was source-filtered out.
Apparently. It's unclear to me why that happened, so I'm proposing this
alternate "fix" to get the buildNoTests to pass.

It would be nice to test more configurations, but this mode of building
is on the way out anyway, so let's just make it pass and see what
configurations make sense to test as part of the meson migration.

flake.nix

@@ -143,6 +143,7 @@
 
           nix_noTests = final.nix.override {
             doInstallCheck = false;
+            doCheck = false;
           };
 
           # See https://github.com/NixOS/nixpkgs/pull/214409