Do not interpose //external:cc_toolchain when depending on the locally-generated C++ toolchain.

RELNOTES: None.
PiperOrigin-RevId: 305470868
diff --git a/tools/cpp/BUILD.tools b/tools/cpp/BUILD.tools
index c936d27..dc72e23 100644
--- a/tools/cpp/BUILD.tools
+++ b/tools/cpp/BUILD.tools
@@ -92,7 +92,7 @@
 #   * all file groups that said cc_toolchain might refer to
 alias(
     name = "toolchain",
-    actual = "//external:cc_toolchain",
+    actual = "@local_config_cc//:toolchain",
 )
 
 # Hardcoded toolchain, legacy behaviour.