unix Makefile: -Og doesn't work (at least) with gcc 4.6 below.

Also, don't try to force debug info format, use native.

unix/Makefile

@@ -15,7 +15,7 @@ LDFLAGS = -lm
 
 #Debugging/Optimization
 ifdef DEBUG
-CFLAGS += -Og -ggdb
+CFLAGS += -O0 -g
 else
 CFLAGS += -Os #-DNDEBUG
 endif