Rename PREFIX to DATADIR as its purpose is only to find data files (avoids
conflicts with our PREFIX, which has another meaning).
Do not enforce compilers.

--- Makefile.orig	2014-01-07 08:52:28.000000000 +0100
+++ Makefile	2014-11-17 19:05:21.738720856 +0100
@@ -14,7 +14,7 @@
 RELEASE ?= 1
 
 # Base path of app installation
-PREFIX ?= /usr/local/share/games/jfsw
+DATADIR ?= /usr/local/share/games/jfsw
 
 # DirectX SDK location
 DXROOT ?= $(USERPROFILE)/sdks/directx/dx81
@@ -61,8 +61,8 @@
 
 include $(AUDIOLIBROOT)/Makefile.shared
 
-CC=gcc
-CXX=g++
+CC?=gcc
+CXX?=g++
 OURCFLAGS=$(debug) -W -Wall -Wimplicit -Wno-unused \
 	-fno-pic -fno-strict-aliasing -DNO_GCC_BUILTINS \
 	-I$(INC) -I$(EINC) -I$(MACTROOT) -I$(AUDIOLIBROOT)/include
@@ -165,6 +165,10 @@
 	NASMFLAGS+= -f elf
 	GAMELIBS+= $(JFAUDIOLIB_LDFLAGS)
 endif
+ifeq ($(PLATFORM),BSD)
+	NASMFLAGS+= -f elf
+	GAMELIBS+= $(JFAUDIOLIB_LDFLAGS)
+endif
 ifeq ($(PLATFORM),WINDOWS)
 	OURCFLAGS+= -I$(DXROOT)/include
 	NASMFLAGS+= -f win32 --prefix _
@@ -192,7 +196,7 @@
 OURCFLAGS+= $(BUILDCFLAGS)
 
 ifneq ($(PLATFORM),WINDOWS)
-	OURCFLAGS+= -DPREFIX=\"$(PREFIX)\"
+	OURCFLAGS+= -DDATADIR=\"$(DATADIR)\"
 endif
 
 .PHONY: clean all engine $(ELIB)/$(ENGINELIB) $(ELIB)/$(EDITORLIB) $(AUDIOLIBROOT)/$(JFAUDIOLIB)