Unable to Build

1. `cd easy-erg`
2. `make -f Makefile.linux`

This fails with

```
ERROR: environment variable 'C2API' must point to the location of the c2api directory
```

`Makefile.linux` says,

```
# the .o files that must be linked to from C2API
C2API_OBJS=$(C2API)/c2api.o $(C2api)/csafe.o $(C2API)/csafe_util.o $(C2API)/debug.o $(C2API)/utils.o
```
Where do I get these files?