Making call to Rscript safe; reducing depedencies on tools

Test case (run from command line):
```text
echo "print('This will fuck : everything up')" > /tmp/Rprofile
export R_PROFILE=/tmp/Rprofile
make
```

The presence of the ":" is important in that string. The call to `make` will terminate with:
```text
> make
make/tests:169: *** multiple target patterns.  Stop.
```

After the fix, the call to `make` returns the normal `help` target.