fix: install-deno target triple missing arch prefix

deno's release assets now include the arch in the filename
(deno-x86_64-unknown-linux-gnu.zip), so the old "unknown-linux-gnu"
string 404'd once the pinned version moved past when deno made that
change. Also adds the missing aarch64-linux case.

dot_local/bin/executable_install-deno

@@ -9,7 +9,8 @@ function get_os () (
     case $(uname -sm) in
         "Darwin x86_64") echo x86_64-apple-darwin ;;
         "Darwin arm64")  echo aarch64-apple-darwin ;;
-        "Linux x86_64")  echo unknown-linux-gnu ;;
+        "Linux x86_64")  echo x86_64-unknown-linux-gnu ;;
+        "Linux aarch64") echo aarch64-unknown-linux-gnu ;;
         *)           >&2 echo "unsupported os: $(uname -s)"; exit 1;;
     esac
 )