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/why-depends.cc b/third_party/nix/src/nix/why-depends.cc
index 4fb91c9d91..e18314e7fd 100644
--- a/third_party/nix/src/nix/why-depends.cc
+++ b/third_party/nix/src/nix/why-depends.cc
@@ -23,7 +23,7 @@ static std::string filterPrintable(const std::string& s) {
   return res;
 }
 
-struct CmdWhyDepends : SourceExprCommand {
+struct CmdWhyDepends final : SourceExprCommand {
   std::string _package, _dependency;
   bool all = false;