Bump tlcpack/package-* images to v0.4

[leandron]

• Update LLVM build to be linked against Python 3.7
• Updates Ethos-N to version 21.08
• Due to the deprecation of Python 3.6, the latest pytorch/manylinux-cuda102 (id 2146d9ccbb6e) is not shipping with cp36, so wheel/build_wheel_manylinux.sh needed some refactoring to cope with versions of Python not in the image.
• All these fixes need to be bundled in a single PR so as to un-break the builds without manual intervention in the git repository.

cc @Leo-arm @areusch @tqchen @Mousius

[Mousius]

Thanks for this @leandron :smile_cat: