Include cpack in Emscripten docker image

[MarkCallow]

• Problematic Docker Image: trzeci/emscripten:sdk-incoming-64bit

Please state what is missing:

1. cpack

This may just be a question rather than an RFI. I need to run cpack to build .zip files of the .js & .wasm built by Emscripten. CMake configuration and build is run in docker, on Travis-CI, by

docker exec -it emscripten sh -c "emcmake cmake -Bbuild-web-release . && cmake --build build-web-release --config Release"

After this, when I run cpack outside docker it can't find its template files which it thinks should be in /opt/.... which is where they are in docker where cmake configuration was done. So I tried

docker exec -it emscripten sh -c "cpack --verbose -G ZIP"

I got sh: 1: cpack: not found. I've just confirmed the docker image only has cmake and ctest. Please add cpack.