Do not copy cargo artifacts into a separate output by default

* Copying the cargo artifacts to their own separate output is a good
  idea *in theory* where each derivation produces bins/libs so that
  other things can depend on them without pulling in the cargo artifacts
  as well
* In practice, it's much more likely that a derivation will produce
  cargo artifacts (to be reused in other build/test steps) XOR produce
  the final binaries
* Therefore _not_ separating the outputs will produce less friction when
  forming dependency trees in the general path (e.g. no more forgetting
  to specify `drv.target`)
* If a caller really wants to install cargo artifacts in a separate
  output, they can easily add the customization themselves

lib/buildWithCargo.nix

@@ -39,7 +39,7 @@ let
         cargoLock = path + /Cargo.lock;
       in
       if builtins.pathExists cargoToml && builtins.pathExists cargoLock
-      then (buildDepsOnly args).target
+      then buildDepsOnly args
       else
         throw ''
           unable to find Cargo.toml and Cargo.lock at ${path}. please ensure one of the following:
@@ -68,7 +68,6 @@ in
   # as including them will make Nix pull in all sources when installing any binaries.
 , doRemapSourcePathPrefix ? true
 , nativeBuildInputs ? [ ]
-, outputs ? [ "out" ]
 , ...
 }@args:
 let
@@ -93,8 +92,6 @@ let
   };
 
   additions = {
-    outputs = outputs ++ lib.optional doCopyTargetToOutput "target";
-
     nativeBuildInputs = nativeBuildInputs ++ [
       cargo
       configureCargoCommonVarsHook

pkgs/copyCargoTargetToOutputHook.sh

@@ -1,7 +1,7 @@
 prepareCargoTargetDirAndCopyToDir() {
   # Allow for calling with customized parameters
   # or fall back to defaults if none are provided
-  local dir="${1:-${target}}"
+  local dir="${1:-${out}}"
   local cargoTargetDir="${2:-${CARGO_TARGET_DIR:-target}}"
   local dest="${dir}/target.tar.zst"
 

tests/compilesFresh.nix

@@ -25,7 +25,7 @@ buildWithCargo {
 
   # NB: explicit call here so that the buildDepsOnly call
   # doesn't inherit our build commands
-  cargoArtifacts = (buildDepsOnly { inherit src; }).target;
+  cargoArtifacts = buildDepsOnly { inherit src; };
 
   nativeBuildInputs = [ jq ];