Mainly, the build system changes consist in organizing the makefile better and
building to a local `ubuntu/' folder, which should then be copied directly to
the PTS system.

Then, the flash test changes consist in checking for a BusException error to not
fall in the trap of continuing on other exceptions occuring in the block of code
under `try'. Also, the flash test is more "modular" in that the gateware
versions to be downloaded can be specified at the beginning of the file.