Add support for aarch64

PiperOrigin-RevId: 673443795
Change-Id: I1c07e011824641e9c67bd6198d7f378e826edb93

cheriot/BUILD

diff --git a/cheriot/BUILD b/cheriot/BUILD
index 4085f38..a08047b 100644
--- a/cheriot/BUILD
+++ b/cheriot/BUILD
@@ -42,6 +42,11 @@
     values = {"cpu": "darwin_arm64"},
 )
 
+config_setting(
+    name = "aarch64",
+    values = {"cpu": "aarch64"},
+)
+
 mpact_isa_decoder(
     name = "riscv_cheriot_isa",
     src = "riscv_cheriot.isa",