luaPackages.sqlite: make it work out of the box

the tests worked because we exported LIBSQLITE. the user had to either set LIBSQLITE himself or set vim.g.sqlite_clib_path. This change overrides vim.g.sqlite_clib_path

pkgs/development/lua-modules/overrides.nix

@@ -678,9 +678,15 @@ in
     doCheck = true;
     nativeCheckInputs = [ final.plenary-nvim neovim-unwrapped ];
 
+    # the plugin loads the library from either the LIBSQLITE env
+    # or the vim.g.sqlite_clib_path variable.
+    postPatch = ''
+      substituteInPlace lua/sqlite/defs.lua \
+        --replace-fail "path = vim.g.sqlite_clib_path" 'path = vim.g.sqlite_clib_path or  "${sqlite.out}/lib/libsqlite3${stdenv.hostPlatform.extensions.sharedLibrary}"'
+    '';
+
     # we override 'luarocks test' because otherwise neovim doesn't find/load the plenary plugin
     checkPhase = ''
-      export LIBSQLITE="${sqlite.out}/lib/libsqlite3${stdenv.hostPlatform.extensions.sharedLibrary}"
       export HOME="$TMPDIR";
 
       nvim --headless -i NONE \