Could be caused by missing dependencies or an incompatibility with the alpine based image you are using. The __WORDSIZE variable is typically defined in the system headers, so it's possible that the required header file is not included or available in the alpine image.

I would say to ensure that all necessary dependencies are installed in the docker image. Review the tgt repository documentation or the build instructions to determine the required dependencies.

Also update the Dockerfile to include the necessary packages or libraries. For alpine based images, you can use apk to install the packages. For example, if you need a package called tgt, you can add this command:

RUN apk add --no-cache tgt

before the git clone command in the Dockerfile.

But again that's an example dig more on tgt repo docs, etc.