--- Makefile.orig
+++ Makefile
@@ -67,7 +67,7 @@
 CC_SunOS=gcc
 CC_Cygwin=cc  
 CC_Darwin=cc  
-CC=$(CC_$(SYSTEM))
+CC?=$(CC_$(SYSTEM))
 
 # C++ compiler mapping
 CPP_hpux=aCC  
@@ -77,7 +77,7 @@
 CPP_SunOS=g++
 CPP_Cygwin=g++  
 CPP_Darwin=g++  
-CPP=$(CPP_$(SYSTEM))
+CPP?=$(CPP_$(SYSTEM))
 
 #Model specific flags
 MFLAGS_ia64=+DD64
@@ -99,7 +99,7 @@
 CFLAGS_SunOS=-g
 CFLAGS_Cygwin=-D__CYGWIN -Dsocklen_t=int
 CFLAGS_Darwin=-D__DARWIN
-CFLAGS=$(CFLAGS_$(SYSTEM)) -D__3PCC__ $(TLS) $(PCAPPLAY)
+CFLAGS+=$(CFLAGS_$(SYSTEM)) -D__3PCC__ $(TLS) $(PCAPPLAY)
 
 #C++ Compiler Flags
 CPPFLAGS_hpux=-AA -mt -D__HPUX +W829 
@@ -109,7 +109,7 @@
 CPPFLAGS_SunOS=-g
 CPPFLAGS_Cygwin=-D__CYGWIN -Dsocklen_t=int
 CPPFLAGS_Darwin=-D__DARWIN
-CPPFLAGS=$(CPPFLAGS_$(SYSTEM)) -D__3PCC__ $(TLS) $(PCAPPLAY)
+CPPFLAGS+=$(CPPFLAGS_$(SYSTEM)) -D__3PCC__ $(TLS) $(PCAPPLAY)
 
 #Linker mapping
 CCLINK_hpux=aCC
@@ -119,7 +119,7 @@
 CCLINK_SunOS=gcc
 CCLINK_Cygwin=g++
 CCLINK_Darwin=g++
-CCLINK=$(CCLINK_$(SYSTEM))
+CCLINK?=$(CCLINK_$(SYSTEM))
 
 #Linker Flags
 LFLAGS_hpux=-AA -mt