[Makefile] keep the CFLAGS declaration

Such that make wouldn't pickup any CFLAGS env var, which happens to be defined in launchpad.
We probably shouldn't even use CFLAGS, since our source is not C... Maybe MLFLAGS or something would be better.

Makefile

@@ -37,7 +37,8 @@ HAXE_INCLUDES=$(HAXE_DIRECTORIES:%=-I _build/src/%)
 EXTLIB_INCLUDES=$(EXTLIB_LIBS:%=-I libs/%)
 ALL_INCLUDES=$(EXTLIB_INCLUDES) $(HAXE_INCLUDES)
 FINDLIB_PACKAGES=$(FINDLIB_LIBS:%=-package %)
-ALL_CFLAGS=-bin-annot -g -w -3 $(ALL_INCLUDES) $(FINDLIB_PACKAGES)
+CFLAGS=
+ALL_CFLAGS=-bin-annot -g -w -3 $(CFLAGS) $(ALL_INCLUDES) $(FINDLIB_PACKAGES)
 
 ifeq ($(BYTECODE),1)
 	TARGET_FLAG = bytecode