Enable aarch64 toolchain for host.

Change-Id: I2d2053361a198ae0027fbaeb279c3c807adc6091
Signed-off-by: Tyler Chatow <tchatow@gmail.com>
diff --git a/WORKSPACE b/WORKSPACE
index 6031ba9..0d9e0f7 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -266,6 +266,7 @@
     },
     toolchain_roots = {
         "linux-x86_64": "@llvm_k8//",
+        "linux-aarch64": "@llvm_aarch64//",
     },
 )