Also made the following other changes:
- The final image for the tool-specific Dockerfiles is based off of
alpine instead of ubuntu
- Add step to build libtatsu, which is a new dependency for
libimobiledevice
- Multithread make operations during build
- Use ARG instead of ENV for build environment variables
- Use apt-get instead of apt
- Use non-dev library in the final image (except for manually built libraries)
