Tweaked Makefile to ignore failure in removing binary in 'clean' target.
Tweaked Makefile to ignore failure in removing binary in 'clean' target.

evaneschneider/cholla,evaneschneider/cholla,cholla-hydro/cholla,cholla-hydro/cholla,evaneschneider/cholla,cholla-hydro/cholla,cholla-hydro/cholla,evaneschneider/cholla