Linux workflow: fix arch test

Author: lool

.github/workflows/linux.yml

@@ -57,7 +57,7 @@ jobs:
         run: |
             set -ux
             # download arm64 package lists to install cross build-dependencies
-            if "$(dpkg --print-architecture != arm64)"; then
+            if [ "$(dpkg --print-architecture)" != arm64 ]; then
                 dpkg --add-architecture arm64
                 apt update
             fi