Building system.bc manually

@schellingb I just tried to manually build the "system/" libraries/headers
on Ubuntu 21.10 (because the prebuilt archives you provide do not work for me, I get <math.h> include error..)
```
$ ls system
include  lib  system.bc
$ make -j 8 -f wajic.mk ./system/system.bc
wajic.mk:90: *** No source files found for build.  Stop.
```

Do you know what's happening, can you help ?