support ARM64 for appliances/mailcatcher
support ARM64 for appliances/mailcatcher

refs DE-1159

Change-Id: Ie5d59138d8dc45a4e20e535fffdaf8bcb2e135fc
Reviewed-on: https://gerrit.instructure.com/c/dockerfiles/+/291129
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
QA-Review: Aaron Ogata <11ccf682c06d1508642f943a3962a1c3d00b8e44@instructure.com>
Reviewed-by: Andrea Cirulli <b4e55ef5ee4bae8ad31f7c81009bfc0af1714a1f@instructure.com>

instructure/dockerfiles,instructure/dockerfiles,instructure/dockerfiles,instructure/dockerfiles