chore: fix buildspec that read env vars incorrectly (#229)

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Author: Lou1415926

buildspec.yml

@@ -22,7 +22,7 @@ phases:
       - make build-image
       - make publish-dockerhub
       - |
-        if [ ARCH_SUFFIX = "amd64" ]; then
+        if [ $ARCH_SUFFIX = "amd64" ]; then
           make tag-latest
           make publish-dockerhub-latest
         fi