Build Issue with RAM Usage (Fix Included)

Hi,

while building the project I ran into a issue while building. All files are compiled in parallel which overuses RAM and can crash a machine.



# Fix

In file https://github.com/jm62300/d4/blob/main/build.sh  (main build file) replace line 40:
```bash
make -j
```
by

```bash
make -j 16
```

That limits the number of jobs to 16 and not infinite. It still compiles reasonably fast (20s)
