fix(3p/nix): Fix all remaining compiler warnings r/1403

This compiles under `-Wall -Werror`.

The largest chunk of this change is `final` qualifiers for the various
Nix CLI command structs, which inherit from a Command class that has
more virtual functions than are implemented by each command.

Change-Id: I0925e6e1a39013f026773db5816e4a77d50f3b4a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1294
Tested-by: BuildkiteCI
Reviewed-by: isomer <isomer@tvl.fyi>
Reviewed-by: kanepyork <rikingcoding@gmail.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/third_party/nix/src/nix/search.cc b/third_party/nix/src/nix/search.cc
index 350863cf81..2bfdeac6f7 100644
--- a/third_party/nix/src/nix/search.cc
+++ b/third_party/nix/src/nix/search.cc
@@ -27,7 +27,7 @@ std::string hilite(const std::string& s, const std::smatch& m,
                          postfix + std::string(m.suffix());
 }
 
-struct CmdSearch : SourceExprCommand, MixJSON {
+struct CmdSearch final : SourceExprCommand, MixJSON {
   std::vector<std::string> res;
 
   bool writeCache = true;