Add loongarch64 support in extension.bzl (#138)

host/extension.bzl

diff --git a/host/extension.bzl b/host/extension.bzl
index 69410cd..49cd45e 100644
--- a/host/extension.bzl
+++ b/host/extension.bzl
@@ -17,6 +17,8 @@
         return "mips64"
     if arch in ["riscv64"]:
         return "riscv64"
+    if arch in ["loongarch64"]:
+        return "loongarch64"
     return None
 
 def _translate_os(os):