Large image size

[kanwren]

The image is currently 4.17GB, and it would help the students out a lot if we shrank it. Some initial things to consider:

• /usr/lib/arm-none-eabi/newlib/thumb takes up an enormous amount of space and might not be needed for what we're doing with GBA
• Cleanup steps for artifacts should run in the same Docker layer that produced them, or they will contribute to the total image size.
• --no-install-recommends could be applied liberally to shave off some unnecessary packages

[sameer-s]

Marking as resolved, see https://github.com/gt-cs2110/cs2110docker/commit/96694a83e4fed041b062d61f0132f3284f583f22 https://github.com/gt-cs2110/cs2110docker/commit/91e5d90e08f8661a6eeac755626697198f8ff5a8