regen-makefile.sh: Increase file Code splitting to decrease mem use

Building MME_Tests with an 8core host with 16GB of RAM sometimes
exhausts the whole available RAM, triggering the OOM killer.
Let's increase the variable to generate 8 C++ files for each TTCN3
files, in order to avoid consuming so much memory.

Change-Id: If5f54e18384f8a26b281d057e9d9f5c450566422
1 file changed