Added optimization to vera binary

[MrLego8-9]

Added basic optimization flags for vera binary

These two simple flags can decrease the runtime by at the very least 25%.
Such an increase makes using the tool less painful for student, but also allows some power savings, like for automated tests...

[emneo-dev]

Do you have some numbers to show that putting O3 instead of O2 for example would give a significant boost in performance?
I see you talk about at least 25% speed-up, how did you find that number?
03 should be safe enough, but I don't know what vera does really in its code so I couldn't really say if it is completely fine.

[MrLego8-9]

Here is a basic benchmark for vera with different optimization level. They go in order No opti > O2 > O3 (they are also specified in the vera binary name).
The 25% is a really low estimation of the speed-up I gave, which you can see is more like a 4x speed-up

[MrLego8-9]

As a note, the command in the benchmarks is the one in the coding-style-checker docker