builder.sh: shellcheck 2129

https://github.com/koalaman/shellcheck/wiki/SC2129

pkgs/stdenv/generic/builder.sh

@@ -6,12 +6,14 @@ done
 
 mkdir "$out"
 
-echo "export SHELL=$shell" > $out/setup
-echo "initialPath=\"$initialPath\"" >> $out/setup
-echo "defaultNativeBuildInputs=\"$defaultNativeBuildInputs\"" >> $out/setup
-echo "defaultBuildInputs=\"$defaultBuildInputs\"" >> $out/setup
-echo "$preHook" >> $out/setup
-cat "$setup" >> $out/setup
+{
+    echo "export SHELL=$shell"
+    echo "initialPath=\"$initialPath\""
+    echo "defaultNativeBuildInputs=\"$defaultNativeBuildInputs\""
+    echo "defaultBuildInputs=\"$defaultBuildInputs\""
+    echo "$preHook"
+    cat "$setup"
+} > "$out/setup"
 
 # Allow the user to install stdenv using nix-env and get the packages
 # in stdenv.