Default condition missing for xnnpack_aggregate_library

[Nayana-ibm]

Default condition is missing for xnnpack_aggregate_library.
This causes TensorFlow build to fail on s390x

[Nayana-ibm]

Below patch adds default condition.

diff --git a/build_defs.bzl b/build_defs.bzl
index db0ee74f2..afec3a98c 100644
--- a/build_defs.bzl
+++ b/build_defs.bzl
@@ -260,6 +260,7 @@ def xnnpack_aggregate_library(
             "//build_config:emscripten_wasmsimd": wasmsimd_deps,
             "//build_config:emscripten_wasmrelaxedsimd": wasmrelaxedsimd_deps,
             "//build_config:riscv": riscv_deps,
+           "//conditions:default": [],
         }),
         defines = defines,
         compatible_with = compatible_with,

Let me know if PR needs to be raised.