Use tmp_unlink to remove temporary file in use_relative_paths_in_depfile

No need to remove via another temporary file.

(cherry picked from commit c74b625)

src/ccache.cpp

@@ -953,7 +953,7 @@ use_relative_paths_in_depfile(const Context& ctx)
   }
   if (!result) {
     cc_log("Removing temporary dependency file: %s", tmp_file);
-    x_unlink(tmp_file);
+    tmp_unlink(tmp_file);
   }
   free(tmp_file);
 }