Building on macOS

Created by: Yoric

This patch:

• increases the size of the redoxfs image, which was too small to accomodate all the data;
• causes all manipulation of files that belong to root to take place in a sudo, as macOS would block them otherwise.

Along with https://github.com/Yoric/redoxfs/commit/0353bfc00c3b9c5351abf32fe60314bc5641165b, this should fix the ability to build the new kernel on macOS.