Allow building module wheels for arm64 linux

[mdevl]

Currently the script dockcross-manylinux-download-cache-and-build-module-wheels.sh only allows to build x86 python wheels. To my understanding it should be possible to also build wheels of a python ITK module for arm64 architecture on a linux machine.

Modifying the user-facing script to allow specifying an architecture different from x86 would be very helpful and greatly appreciated.

[tbirdso]

cc @jcfr @thewtex

[thewtex]

Closed via #228