backend/ninja: fix bad @OUTPUTn@ replacements

`outfilelist` is the output list of the target, while `outfiles` is the output
list of the individual commands

Bug: mesonbuild/pull/13304#issuecomment-2226398671

mesonbuild/backend/ninjabackend.py

@@ -2623,7 +2623,7 @@ def generate_genlist_for_target(self, genlist: build.GeneratedList, target: buil
                 args = [x.replace('@DEPFILE@', depfile) for x in base_args]
             args = [x.replace("@INPUT@", infilename).replace('@OUTPUT@', sole_output)
                     for x in args]
-            args = self.replace_outputs(args, self.get_target_private_dir(target), outfilelist)
+            args = self.replace_outputs(args, self.get_target_private_dir(target), outfiles)
             # We have consumed output files, so drop them from the list of remaining outputs.
             if len(generator.outputs) > 1:
                 outfilelist = outfilelist[len(generator.outputs):]