To fix no toolchain for cpu aarch64.

Author: solderzzc

src/test/shell/bazel/testdata/bazel_toolchain_test_data/tools/arm_compiler/CROSSTOOL

@@ -12,6 +12,10 @@ default_toolchain {
   toolchain_identifier: "local"
 }
 
+default_toolchain {
+  cpu: "aarch64"
+  toolchain_identifier: "local"
+}
 toolchain {
   abi_version: "gcc"
   abi_libc_version: "glibc_2.19"

tools/cpp/CROSSTOOL.tpl

@@ -21,6 +21,10 @@ default_toolchain {
   cpu: "s390x"
   toolchain_identifier: "local"
 }
+default_toolchain {
+  cpu: "aarch64"
+  toolchain_identifier: "local"
+}
 
 default_toolchain {
   cpu: "ios_x86_64"